diff options
Diffstat (limited to 'Documentation')
| -rw-r--r-- | Documentation/accounting/taskstats-struct.txt | 6 | ||||
| -rw-r--r-- | Documentation/auxdisplay/cfag12864b | 4 | ||||
| -rw-r--r-- | Documentation/auxdisplay/cfag12864b-example.c | 2 | ||||
| -rw-r--r-- | Documentation/auxdisplay/ks0108 | 4 | ||||
| -rw-r--r-- | Documentation/cgroups.txt | 4 | ||||
| -rw-r--r-- | Documentation/controllers/devices.txt | 8 | ||||
| -rw-r--r-- | Documentation/cpusets.txt | 9 | ||||
| -rw-r--r-- | Documentation/feature-removal-schedule.txt | 9 | ||||
| -rw-r--r-- | Documentation/ftrace.txt | 1353 | ||||
| -rw-r--r-- | Documentation/i2c/writing-clients | 18 | ||||
| -rw-r--r-- | Documentation/kernel-parameters.txt | 8 | ||||
| -rw-r--r-- | Documentation/networking/ip-sysctl.txt | 12 | ||||
| -rw-r--r-- | Documentation/networking/s2io.txt | 6 | ||||
| -rw-r--r-- | Documentation/video4linux/CARDLIST.au0828 | 2 | ||||
| -rw-r--r-- | Documentation/vm/slabinfo.c | 4 | ||||
| -rw-r--r-- | Documentation/vm/slub.txt | 2 |
16 files changed, 1421 insertions, 30 deletions
diff --git a/Documentation/accounting/taskstats-struct.txt b/Documentation/accounting/taskstats-struct.txt index 8aa7529f8258..cd784f46bf8a 100644 --- a/Documentation/accounting/taskstats-struct.txt +++ b/Documentation/accounting/taskstats-struct.txt @@ -24,6 +24,8 @@ There are three different groups of fields in the struct taskstats: 4) Per-task and per-thread context switch count statistics +5) Time accounting for SMT machines + Future extension should add fields to the end of the taskstats struct, and should not change the relative position of each field within the struct. @@ -164,4 +166,8 @@ struct taskstats { __u64 nvcsw; /* Context voluntary switch counter */ __u64 nivcsw; /* Context involuntary switch counter */ +5) Time accounting for SMT machines + __u64 ac_utimescaled; /* utime scaled on frequency etc */ + __u64 ac_stimescaled; /* stime scaled on frequency etc */ + __u64 cpu_scaled_run_real_total; /* scaled cpu_run_real_total */ } diff --git a/Documentation/auxdisplay/cfag12864b b/Documentation/auxdisplay/cfag12864b index b714183d4125..eb7be393a510 100644 --- a/Documentation/auxdisplay/cfag12864b +++ b/Documentation/auxdisplay/cfag12864b @@ -3,7 +3,7 @@ =================================== License: GPLv2 -Author & Maintainer: Miguel Ojeda Sandonis <maxextreme@gmail.com> +Author & Maintainer: Miguel Ojeda Sandonis Date: 2006-10-27 @@ -22,7 +22,7 @@ Date: 2006-10-27 1. DRIVER INFORMATION --------------------- -This driver support one cfag12864b display at time. +This driver supports a cfag12864b LCD. --------------------- diff --git a/Documentation/auxdisplay/cfag12864b-example.c b/Documentation/auxdisplay/cfag12864b-example.c index 7bfac354d4c9..2caeea5e4993 100644 --- a/Documentation/auxdisplay/cfag12864b-example.c +++ b/Documentation/auxdisplay/cfag12864b-example.c @@ -4,7 +4,7 @@ * Description: cfag12864b LCD userspace example program * License: GPLv2 * - * Author: Copyright (C) Miguel Ojeda Sandonis <maxextreme@gmail.com> + * Author: Copyright (C) Miguel Ojeda Sandonis * Date: 2006-10-31 * * This program is free software; you can redistribute it and/or modify diff --git a/Documentation/auxdisplay/ks0108 b/Documentation/auxdisplay/ks0108 index 92b03b60c613..8ddda0c8ceef 100644 --- a/Documentation/auxdisplay/ks0108 +++ b/Documentation/auxdisplay/ks0108 @@ -3,7 +3,7 @@ ========================================== License: GPLv2 -Author & Maintainer: Miguel Ojeda Sandonis <maxextreme@gmail.com> +Author & Maintainer: Miguel Ojeda Sandonis Date: 2006-10-27 @@ -21,7 +21,7 @@ Date: 2006-10-27 1. DRIVER INFORMATION --------------------- -This driver support the ks0108 LCD controller. +This driver supports the ks0108 LCD controller. --------------------- diff --git a/Documentation/cgroups.txt b/Documentation/cgroups.txt index 824fc0274471..d9014aa0eb68 100644 --- a/Documentation/cgroups.txt +++ b/Documentation/cgroups.txt @@ -390,6 +390,10 @@ If you have several tasks to attach, you have to do it one after another: ... # /bin/echo PIDn > tasks +You can attach the current shell task by echoing 0: + +# echo 0 > tasks + 3. Kernel API ============= diff --git a/Documentation/controllers/devices.txt b/Documentation/controllers/devices.txt index 4dcea42432c2..7cc6e6a60672 100644 --- a/Documentation/controllers/devices.txt +++ b/Documentation/controllers/devices.txt @@ -13,7 +13,7 @@ either an integer or * for all. Access is a composition of r The root device cgroup starts with rwm to 'all'. A child device cgroup gets a copy of the parent. Administrators can then remove devices from the whitelist or add new entries. A child cgroup can -never receive a device access which is denied its parent. However +never receive a device access which is denied by its parent. However when a device access is removed from a parent it will not also be removed from the child(ren). @@ -29,7 +29,11 @@ allows cgroup 1 to read and mknod the device usually known as echo a > /cgroups/1/devices.deny -will remove the default 'a *:* mrw' entry. +will remove the default 'a *:* rwm' entry. Doing + + echo a > /cgroups/1/devices.allow + +will add the 'a *:* rwm' entry to the whitelist. 3. Security diff --git a/Documentation/cpusets.txt b/Documentation/cpusets.txt index 353504de3084..1f5a924d1e56 100644 --- a/Documentation/cpusets.txt +++ b/Documentation/cpusets.txt @@ -154,13 +154,15 @@ browsing and modifying the cpusets presently known to the kernel. No new system calls are added for cpusets - all support for querying and modifying cpusets is via this cpuset file system. -The /proc/<pid>/status file for each task has two added lines, +The /proc/<pid>/status file for each task has four added lines, displaying the tasks cpus_allowed (on which CPUs it may be scheduled) and mems_allowed (on which Memory Nodes it may obtain memory), -in the format seen in the following example: +in the two formats seen in the following example: Cpus_allowed: ffffffff,ffffffff,ffffffff,ffffffff + Cpus_allowed_list: 0-127 Mems_allowed: ffffffff,ffffffff + Mems_allowed_list: 0-63 Each cpuset is represented by a directory in the cgroup file system containing (on top of the standard cgroup files) the following @@ -544,6 +546,9 @@ otherwise initial value -1 that indicates the cpuset has no request. ( 4 : search nodes in a chunk of node [on NUMA system] ) ( 5 : search system wide [on NUMA system] ) +The system default is architecture dependent. The system default +can be changed using the relax_domain_level= boot parameter. + This file is per-cpuset and affect the sched domain where the cpuset belongs to. Therefore if the flag 'sched_load_balance' of a cpuset is disabled, then 'sched_relax_domain_level' have no effect since diff --git a/Documentation/feature-removal-schedule.txt b/Documentation/feature-removal-schedule.txt index 5b3f31faed56..46ece3fba6f9 100644 --- a/Documentation/feature-removal-schedule.txt +++ b/Documentation/feature-removal-schedule.txt @@ -312,3 +312,12 @@ When: 2.6.26 Why: Implementation became generic; users should now include linux/semaphore.h instead. Who: Matthew Wilcox <willy@linux.intel.com> + +--------------------------- + +What: CONFIG_THERMAL_HWMON +When: January 2009 +Why: This option was introduced just to allow older lm-sensors userspace + to keep working over the upgrade to 2.6.26. At the scheduled time of + removal fixed lm-sensors (2.x or 3.x) should be readily available. +Who: Rene Herman <rene.herman@gmail.com> diff --git a/Documentation/ftrace.txt b/Documentation/ftrace.txt new file mode 100644 index 000000000000..13e4bf054c38 --- /dev/null +++ b/Documentation/ftrace.txt @@ -0,0 +1,1353 @@ + ftrace - Function Tracer + ======================== + +Copyright 2008 Red Hat Inc. +Author: Steven Rostedt <srostedt@redhat.com> + + +Introduction +------------ + +Ftrace is an internal tracer designed to help out developers and +designers of systems to find what is going on inside the kernel. +It can be used for debugging or analyzing latencies and performance +issues that take place outside of user-space. + +Although ftrace is the function tracer, it also includes an +infrastructure that allows for other types of tracing. Some of the +tracers that are currently in ftrace is a tracer to trace +context switches, the time it takes for a high priority task to +run after it was woken up, the time interrupts are disabled, and +more. + + +The File System +--------------- + +Ftrace uses the debugfs file system to hold the control files as well +as the files to display output. + +To mount the debugfs system: + + # mkdir /debug + # mount -t debugfs nodev /debug + + +That's it! (assuming that you have ftrace configured into your kernel) + +After mounting the debugfs, you can see a directory called +"tracing". This directory contains the control and output files +of ftrace. Here is a list of some of the key files: + + + Note: all time values are in microseconds. + + current_tracer : This is used to set or display the current tracer + that is configured. + + available_tracers : This holds the different types of tracers that + has been compiled into the kernel. The tracers + listed here can be configured by echoing in their + name into current_tracer. + + tracing_enabled : This sets or displays whether the current_tracer + is activated and tracing or not. Echo 0 into this + file to disable the tracer or 1 (or non-zero) to + enable it. + + trace : This file holds the output of the trace in a human readable + format. + + latency_trace : This file shows the same trace but the information + is organized more to display possible latencies + in the system. + + trace_pipe : The output is the same as the "trace" file but this + file is meant to be streamed with live tracing. + Reads from this file will block until new data + is retrieved. Unlike the "trace" and "latency_trace" + files, this file is a consumer. This means reading + from this file causes sequential reads to display + more current data. Once data is read from this + file, it is consumed, and will not be read + again with a sequential read. The "trace" and + "latency_trace" files are static, and if the + tracer isn't adding more data, they will display + the same information every time they are read. + + iter_ctrl : This file lets the user control the amount of data + that is displayed in one of the above output + files. + + trace_max_latency : Some of the tracers record the max latency. + For example, the time interrupts are disabled. + This time is saved in this file. The max trace + will also be stored, and displayed by either + "trace" or "latency_trace". A new max trace will + only be recorded if the latency is greater than + the value in this file. (in microseconds) + + trace_entries : This sets or displays the number of trace + entries each CPU buffer can hold. The tracer buffers + are the same size for each CPU, so care must be + taken when modifying the trace_entries. The number + of actually entries will be the number given + times the number of possible CPUS. The buffers + are saved as individual pages, and the actual entries + will always be rounded up to entries per page. + + This can only be updated when the current_tracer + is set to "none". + + NOTE: It is planned on changing the allocated buffers + from being the number of possible CPUS to + the number of online CPUS. + + tracing_cpumask : This is a mask that lets the user only trace + on specified CPUS. The format is a hex string + representing the CPUS. + + set_ftrace_filter : When dynamic ftrace is configured in, the + code is dynamically modified to disable calling + of the function profiler (mcount). This lets + tracing be configured in with practically no overhead + in performance. This also has a side effect of + enabling or disabling specific functions to be + traced. Echoing in names of functions into this + file will limit the trace to only those files. + + set_ftrace_notrace: This has the opposite effect that + set_ftrace_filter has. Any function that is added + here will not be traced. If a function exists + in both set_ftrace_filter and set_ftrace_notrace + the function will _not_ bet traced. + + available_filter_functions : When a function is encountered the first + time by the dynamic tracer, it is recorded and + later the call is converted into a nop. This file + lists the functions that have been recorded + by the dynamic tracer and these functions can + be used to set the ftrace filter by the above + "set_ftrace_filter" file. + + +The Tracers +----------- + +Here are the list of current tracers that can be configured. + + ftrace - function tracer that uses mcount to trace all functions. + It is possible to filter out which functions that are + traced when dynamic ftrace is configured in. + + sched_switch - traces the context switches between tasks. + + irqsoff - traces the areas that disable interrupts and saves off + the trace with the longest max latency. + See tracing_max_latency. When a new max is recorded, + it replaces the old trace. It is best to view this + trace with the latency_trace file. + + preemptoff - Similar to irqsoff but traces and records the time + preemption is disabled. + + preemptirqsoff - Similar to irqsoff and preemptoff, but traces and + records the largest time irqs and/or preemption is + disabled. + + wakeup - Traces and records the max latency that it takes for + the highest priority task to get scheduled after + it has been woken up. + + none - This is not a tracer. To remove all tracers from tracing + simply echo "none" into current_tracer. + + +Examples of using the tracer +---------------------------- + +Here are typical examples of using the tracers with only controlling +them with the debugfs interface (without using any user-land utilities). + +Output format: +-------------- + +Here's an example of the output format of the file "trace" + + -------- +# tracer: ftrace +# +# TASK-PID CPU# TIMESTAMP FUNCTION +# | | | | | + bash-4251 [01] 10152.583854: path_put <-path_walk + bash-4251 [01] 10152.583855: dput <-path_put + bash-4251 [01] 10152.583855: _atomic_dec_and_lock <-dput + -------- + +A header is printed with the trace that is represented. In this case +the tracer is "ftrace". Then a header showing the format. Task name +"bash", the task PID "4251", the CPU that it was running on +"01", the timestamp in <secs>.<usecs> format, the function name that was +traced "path_put" and the parent function that called this function +"path_walk". + +The sched_switch tracer also includes tracing of task wake ups and +context switches. + + ksoftirqd/1-7 [01] 1453.070013: 7:115:R + 2916:115:S + ksoftirqd/1-7 [01] 1453.070013: 7:115:R + 10:115:S + ksoftirqd/1-7 [01] 1453.070013: 7:115:R ==> 10:115:R + events/1-10 [01] 1453.070013: 10:115:S ==> 2916:115:R + kondemand/1-2916 [01] 1453.070013: 2916:115:S ==> 7:115:R + ksoftirqd/1-7 [01] 1453.070013: 7:115:S ==> 0:140:R + +Wake ups are represented by a "+" and the context switches show +"==>". The format is: + + Context switches: + + Previous task Next Task + + <pid>:<prio>:<state> ==> <pid>:<prio>:<state> + + Wake ups: + + Current task Task waking up + + <pid>:<prio>:<state> + <pid>:<prio>:<state> + +The prio is the internal kernel priority, which is inverse to the +priority that is usually displayed by user-space tools. Zero represents +the highest priority (99). Prio 100 starts the "nice" priorities with +100 being equal to nice -20 and 139 being nice 19. The prio "140" is +reserved for the idle task which is the lowest priority thread (pid 0). + + +Latency trace format +-------------------- + +For traces that display latency times, the latency_trace file gives +a bit more information to see why a latency happened. Here's a typical +trace. + +# tracer: irqsoff +# +irqsoff latency trace v1.1.5 on 2.6.26-rc8 +-------------------------------------------------------------------- + latency: 97 us, #3/3, CPU#0 | (M:preempt VP:0, KP:0, SP:0 HP:0 #P:2) + ----------------- + | task: swapper-0 (uid:0 nice:0 policy:0 rt_prio:0) + ----------------- + => started at: apic_timer_interrupt + => ended at: do_softirq + +# _------=> CPU# +# / _-----=> irqs-off +# | / _----=> need-resched +# || / _---=> hardirq/softirq +# ||| / _--=> preempt-depth +# |||| / +# ||||| delay +# cmd pid ||||| time | caller +# \ / ||||| \ | / + <idle>-0 0d..1 0us+: trace_hardirqs_off_thunk (apic_timer_interrupt) + <idle>-0 0d.s. 97us : __do_softirq (do_softirq) + <idle>-0 0d.s1 98us : trace_hardirqs_on (do_softirq) + + +vim:ft=help + + +This shows that the current tracer is "irqsoff" tracing the time +interrupts are disabled. It gives the trace version and the kernel +this was executed on (2.6.26-rc8). Then it displays the max latency +in microsecs (97 us). The number of trace entries displayed +by the total number recorded (both are three: #3/3). The type of +preemption that was used (PREEMPT). VP, KP, SP, and HP are always zero +and reserved for later use. #P is the number of online CPUS (#P:2). + +The task is the process that was running when the latency happened. +(swapper pid: 0). + +The start and stop that caused the latencies: + + apic_timer_interrupt is where the interrupts were disabled. + do_softirq is where they were enabled again. + +The next lines after the header are the trace itself. The header +explains which is which. + + cmd: The name of the process in the trace. + + pid: The PID of that process. + + CPU#: The CPU that the process was running on. + + irqs-off: 'd' interrupts are disabled. '.' otherwise. + + need-resched: 'N' task need_resched is set, '.' otherwise. + + hardirq/softirq: + 'H' - hard irq happened inside a softirq. + 'h' - hard irq is running + 's' - soft irq is running + '.' - normal context. + + preempt-depth: The level of preempt_disabled + +The above is mostly meaningful for kernel developers. + + time: This differs from the trace output where as the trace output + contained a absolute timestamp. This timestamp is relative + to the start of the first entry in the the trace. + + delay: This is just to help catch your eye a bit better. And + needs to be fixed to be only relative to the same CPU. + The marks is determined by the difference between this + current trace and the next trace. + '!' - greater than preempt_mark_thresh (default 100) + '+' - greater than 1 microsecond + ' ' - less than or equal to 1 microsecond. + + The rest is the same as the 'trace' file. + + +iter_ctrl +--------- + +The iter_ctrl file is used to control what gets printed in the trace +output. To see what is available, simply cat the file: + + cat /debug/tracing/iter_ctrl + print-parent nosym-offset nosym-addr noverbose noraw nohex nobin \ + noblock nostacktrace nosched-tree + +To disable one of the options, echo in the option appended with "no". + + echo noprint-parent > /debug/tracing/iter_ctrl + +To enable an option, leave off the "no". + + echo sym-offest > /debug/tracing/iter_ctrl + +Here are the available options: + + print-parent - On function traces, display the calling function + as well as the function being traced. + + print-parent: + bash-4000 [01] 1477.606694: simple_strtoul <-strict_strtoul + + noprint-parent: + bash-4000 [01] 1477.606694: simple_strtoul + + + sym-offset - Display not only the function name, but also the offset + in the function. For example, instead of seeing just + "ktime_get" you will see "ktime_get+0xb/0x20" + + sym-offset: + bash-4000 [01] 1477.606694: simple_strtoul+0x6/0xa0 + + sym-addr - this will also display the function address as well as + the function name. + + sym-addr: + bash-4000 [01] 1477.606694: simple_strtoul <c0339346> + + verbose - This deals with the latency_trace file. + + bash 4000 1 0 00000000 00010a95 [58127d26] 1720.415ms \ + (+0.000ms): simple_strtoul (strict_strtoul) + + raw - This will display raw numbers. This option is best for use with + user applications that can translate the raw numbers better than + having it done in the kernel. + + hex - similar to raw, but the numbers will be in a hexadecimal format. + + bin - This will print out the formats in raw binary. + + block - TBD (needs update) + + stacktrace - This is one of the options that changes the trace itself. + When a trace is recorded, so is the stack of functions. + This allows for back traces of trace sites. + + sched-tree - TBD (any users??) + + +sched_switch +------------ + +This tracer simply records schedule switches. Here's an example +on how to implement it. + + # echo sched_switch > /debug/tracing/current_tracer + # echo 1 > /debug/tracing/tracing_enabled + # sleep 1 + # echo 0 > /debug/tracing/tracing_enabled + # cat /debug/tracing/trace + +# tracer: sched_switch +# +# TASK-PID CPU# TIMESTAMP FUNCTION +# | | | | | + bash-3997 [01] 240.132281: 3997:120:R + 4055:120:R + bash-3997 [01] 240.132284: 3997:120:R ==> 4055:120:R + sleep-4055 [01] 240.132371: 4055:120:S ==> 3997:120:R + bash-3997 [01] 240.132454: 3997:120:R + 4055:120:S + bash-3997 [01] 240.132457: 3997:120:R ==> 4055:120:R + sleep-4055 [01] 240.132460: 4055:120:D ==> 3997:120:R + bash-3997 [01] 240.132463: 3997:120:R + 4055:120:D + bash-3997 [01] 240.132465: 3997:120:R ==> 4055:120:R + <idle>-0 [00] 240.132589: 0:140:R + 4:115:S + <idle>-0 [00] 240.132591: 0:140:R ==> 4:115:R + ksoftirqd/0-4 [00] 240.132595: 4:115:S ==> 0:140:R + <idle>-0 [00] 240.132598: 0:140:R + 4:115:S + <idle>-0 [00] 240.132599: 0:140:R ==> 4:115:R + ksoftirqd/0-4 [00] 240.132603: 4:115:S ==> 0:140:R + sleep-4055 [01] 240.133058: 4055:120:S ==> 3997:120:R + [...] + + +As we have discussed previously about this format, the header shows +the name of the trace and points to the options. The "FUNCTION" +is a misnomer since here it represents the wake ups and context +switches. + +The sched_switch only lists the wake ups (represented with '+') +and context switches ('==>') with the previous task or current +first followed by the next task or task waking up. The format for both +of these is PID:KERNEL-PRIO:TASK-STATE. Remember that the KERNEL-PRIO +is the inverse of the actual priority with zero (0) being the highest +priority and the nice values starting at 100 (nice -20). Below is +a quick chart to map the kernel priority to user land priorities. + + Kernel priority: 0 to 99 ==> user RT priority 99 to 0 + Kernel priority: 100 to 139 ==> user nice -20 to 19 + Kernel priority: 140 ==> idle task priority + +The task states are: + + R - running : wants to run, may not actually be running + S - sleep : process is waiting to be woken up (handles signals) + D - deep sleep : process must be woken up (ignores signals) + T - stopped : process suspended + t - traced : process is being traced (with something like gdb) + Z - zombie : process waiting to be cleaned up + X - unknown + + +ftrace_enabled +-------------- + +The following tracers give different output depending on whether +or not the sysctl ftrace_enabled is set. To set ftrace_enabled, +one can either use the sysctl function or set it via the proc +file system interface. + + sysctl kernel.ftrace_enabled=1 + + or + + echo 1 > /proc/sys/kernel/ftrace_enabled + +To disable ftrace_enabled simply replace the '1' with '0' in +the above commands. + +When ftrace_enabled is set the tracers will also record the functions +that are within the trace. The descriptions of the tracers +will also show an example with ftrace enabled. + + +irqsoff +------- + +When interrupts are disabled, the CPU can not react to any other +external event (besides NMIs and SMIs). This prevents the timer +interrupt from triggering or the mouse interrupt from letting the +kernel know of a new mouse event. The result is a latency with the +reaction time. + +The irqsoff tracer tracks the time interrupts are disabled and when +they are re-enabled. When a new maximum latency is hit, it saves off +the trace so that it may be retrieved at a later time. Every time a +new maximum in reached, the old saved trace is discarded and the new +trace is saved. + +To reset the maximum, echo 0 into tracing_max_latency. Here's an +example: + + # echo irqsoff > /debug/tracing/current_tracer + # echo 0 > /debug/tracing/tracing_max_latency + # echo 1 > /debug/tracing/tracing_enabled + # ls -ltr + [...] + # echo 0 > /debug/tracing/tracing_enabled + # cat /debug/tracing/latency_trace +# tracer: irqsoff +# +irqsoff latency trace v1.1.5 on 2.6.26-rc8 +-------------------------------------------------------------------- + latency: 6 us, #3/3, CPU#1 | (M:preempt VP:0, KP:0, SP:0 HP:0 #P:2) + ----------------- + | task: bash-4269 (uid:0 nice:0 policy:0 rt_prio:0) + ----------------- + => started at: copy_page_range + => ended at: copy_page_range + +# _------=> CPU# +# / _-----=> irqs-off +# | / _----=> need-resched +# || / _---=> hardirq/softirq +# ||| / _--=> preempt-depth +# |||| / +# ||||| delay +# cmd pid ||||| time | caller +# \ / ||||| \ | / + bash-4269 1...1 0us+: _spin_lock (copy_page_range) + bash-4269 1...1 7us : _spin_unlock (copy_page_range) + bash-4269 1...2 7us : trace_preempt_on (copy_page_range) + + +vim:ft=help + +Here we see that that we had a latency of 6 microsecs (which is +very good). The spin_lock in copy_page_range disabled interrupts. +The difference between the 6 and the displayed timestamp 7us is +because the clock must have incremented between the time of recording +the max latency and recording the function that had that latency. + +Note the above had ftrace_enabled not set. If we set the ftrace_enabled +we get a much larger output: + +# tracer: irqsoff +# +irqsoff latency trace v1.1.5 on 2.6.26-rc8 +-------------------------------------------------------------------- + latency: 50 us, #101/101, CPU#0 | (M:preempt VP:0, KP:0, SP:0 HP:0 #P:2) + ----------------- + | task: ls-4339 (uid:0 nice:0 policy:0 rt_prio:0) + ----------------- + => started at: __alloc_pages_internal + => ended at: __alloc_pages_internal + +# _------=> CPU# +# / _-----=> irqs-off +# | / _----=> need-resched +# || / _---=> hardirq/softirq +# ||| / _--=> preempt-depth +# |||| / +# ||||| delay +# cmd pid ||||| time | caller +# \ / ||||| \ | / + ls-4339 0...1 0us+: get_page_from_freelist (__alloc_pages_internal) + ls-4339 0d..1 3us : rmqueue_bulk (get_page_from_freelist) + ls-4339 0d..1 3us : _spin_lock (rmqueue_bulk) + ls-4339 0d..1 4us : add_preempt_count (_spin_lock) + ls-4339 0d..2 4us : __rmqueue (rmqueue_bulk) + ls-4339 0d..2 5us : __rmqueue_smallest (__rmqueue) + ls-4339 0d..2 5us : __mod_zone_page_state (__rmqueue_smallest) + ls-4339 0d..2 6us : __rmqueue (rmqueue_bulk) + ls-4339 0d..2 6us : __rmqueue_smallest (__rmqueue) + ls-4339 0d..2 7us : __mod_zone_page_state (__rmqueue_smallest) + ls-4339 0d..2 7us : __rmqueue (rmqueue_bulk) + ls-4339 0d..2 8us : __rmqueue_smallest (__rmqueue) +[...] + ls-4339 0d..2 46us : __rmqueue_smallest (__rmqueue) + ls-4339 0d..2 47us : __mod_zone_page_state (__rmqueue_smallest) + ls-4339 0d..2 47us : __rmqueue (rmqueue_bulk) + ls-4339 0d..2 48us : __rmqueue_smallest (__rmqueue) + ls-4339 0d..2 48us : __mod_zone_page_state (__rmqueue_smallest) + ls-4339 0d..2 49us : _spin_unlock (rmqueue_bulk) + ls-4339 0d..2 49us : sub_preempt_count (_spin_unlock) + ls-4339 0d..1 50us : get_page_from_freelist (__alloc_pages_internal) + ls-4339 0d..2 51us : trace_hardirqs_on (__alloc_pages_internal) + + +vim:ft=help + + +Here we traced a 50 microsecond latency. But we also see all the +functions that were called during that time. Note that enabling +function tracing we endure an added overhead. This overhead may +extend the latency times. But never the less, this trace has provided +some very helpful debugging. + + +preemptoff +---------- + +When preemption is disabled we may be able to receive interrupts but +the task can not be preempted and a higher priority task must wait +for preemption to be enabled again before it can preempt a lower +priority task. + +The preemptoff tracer traces the places that disables preemption. +Like the irqsoff, it records the maximum latency that preemption +was disabled. The control of preemptoff is much like the irqsoff. + + # echo preemptoff > /debug/tracing/current_tracer + # echo 0 > /debug/tracing/tracing_max_latency + # echo 1 > /debug/tracing/tracing_enabled + # ls -ltr + [...] + # echo 0 > /debug/tracing/tracing_enabled + # cat /debug/tracing/latency_trace +# tracer: preemptoff +# +preemptoff latency trace v1.1.5 on 2.6.26-rc8 +-------------------------------------------------------------------- + latency: 29 us, #3/3, CPU#0 | (M:preempt VP:0, KP:0, SP:0 HP:0 #P:2) + ----------------- + | task: sshd-4261 (uid:0 nice:0 policy:0 rt_prio:0) + ----------------- + => started at: do_IRQ + => ended at: __do_softirq + +# _------=> CPU# +# / _-----=> irqs-off +# | / _----=> need-resched +# || / _---=> hardirq/softirq +# ||| / _--=> preempt-depth +# |||| / +# ||||| delay +# cmd pid ||||| time | caller +# \ / ||||| \ | / + sshd-4261 0d.h. 0us+: irq_enter (do_IRQ) + sshd-4261 0d.s. 29us : _local_bh_enable (__do_softirq) + sshd-4261 0d.s1 30us : trace_preempt_on (__do_softirq) + + +vim:ft=help + +This has some more changes. Preemption was disabled when an interrupt +came in (notice the 'h'), and was enabled while doing a softirq. +(notice the 's'). But we also see that interrupts have been disabled +when entering the preempt off section and leaving it (the 'd'). +We do not know if interrupts were enabled in the mean time. + +# tracer: preemptoff +# +preemptoff latency trace v1.1.5 on 2.6.26-rc8 +-------------------------------------------------------------------- + latency: 63 us, #87/87, CPU#0 | (M:preempt VP:0, KP:0, SP:0 HP:0 #P:2) + ----------------- + | task: sshd-4261 (uid:0 nice:0 policy:0 rt_prio:0) + ----------------- + => started at: remove_wait_queue + => ended at: __do_softirq + +# _------=> CPU# +# / _-----=> irqs-off +# | / _----=> need-resched +# || / _---=> hardirq/softirq +# ||| / _--=> preempt-depth +# |||| / +# ||||| delay +# cmd pid ||||| time | caller +# \ / ||||| \ | / + sshd-4261 0d..1 0us : _spin_lock_irqsave (remove_wait_queue) + sshd-4261 0d..1 1us : _spin_unlock_irqrestore (remove_wait_queue) + sshd-4261 0d..1 2us : do_IRQ (common_interrupt) + sshd-4261 0d..1 2us : irq_enter (do_IRQ) + sshd-4261 0d..1 2us : idle_cpu (irq_enter) + sshd-4261 0d..1 3us : add_preempt_count (irq_enter) + sshd-4261 0d.h1 3us : idle_cpu (irq_enter) + sshd-4261 0d.h. 4us : handle_fasteoi_irq (do_IRQ) +[...] + sshd-4261 0d.h. 12us : add_preempt_count (_spin_lock) + sshd-4261 0d.h1 12us : ack_ioapic_quirk_irq (handle_fasteoi_irq) + sshd-4261 0d.h1 13us : move_native_irq (ack_ioapic_quirk_irq) + sshd-4261 0d.h1 13us : _spin_unlock (handle_fasteoi_irq) + sshd-4261 0d.h1 14us : sub_preempt_count (_spin_unlock) + sshd-4261 0d.h1 14us : irq_exit (do_IRQ) + sshd-4261 0d.h1 15us : sub_preempt_count (irq_exit) + sshd-4261 0d..2 15us : do_softirq (irq_exit) + sshd-4261 0d... 15us : __do_softirq (do_softirq) + sshd-4261 0d... 16us : __local_bh_disable (__do_softirq) + sshd-4261 0d... 16us+: add_preempt_count (__local_bh_disable) + sshd-4261 0d.s4 20us : add_preempt_count (__local_bh_disable) + sshd-4261 0d.s4 21us : sub_preempt_count (local_bh_enable) + sshd-4261 0d.s5 21us : sub_preempt_count (local_bh_enable) +[...] + sshd-4261 0d.s6 41us : add_preempt_count (__local_bh_disable) + sshd-4261 0d.s6 42us : sub_preempt_count (local_bh_enable) + sshd-4261 0d.s7 42us : sub_preempt_count (local_bh_enable) + sshd-4261 0d.s5 43us : add_preempt_count (__local_bh_disable) + sshd-4261 0d.s5 43us : sub_preempt_count (local_bh_enable_ip) + sshd-4261 0d.s6 44us : sub_preempt_count (local_bh_enable_ip) + sshd-4261 0d.s5 44us : add_preempt_count (__local_bh_disable) + sshd-4261 0d.s5 45us : sub_preempt_count (local_bh_enable) +[...] + sshd-4261 0d.s. 63us : _local_bh_enable (__do_softirq) + sshd-4261 0d.s1 64us : trace_preempt_on (__do_softirq) + + +The above is an example of the preemptoff trace with ftrace_enabled +set. Here we see that interrupts were disabled the entire time. +The irq_enter code lets us know that we entered an interrupt 'h'. +Before that, the functions being traced still show that it is not +in an interrupt, but we can see by the functions themselves that +this is not the case. + +Notice that the __do_softirq when called doesn't have a preempt_count. +It may seem that we missed a preempt enabled. What really happened +is that the preempt count is held on the threads stack and we +switched to the softirq stack (4K stacks in effect). The code +does not copy the preempt count, but because interrupts are disabled +we don't need to worry about it. Having a tracer like this is good +to let people know what really happens inside the kernel. + + +preemptirqsoff +-------------- + +Knowing the locations that have interrupts disabled or preemption +disabled for the longest times is helpful. But sometimes we would +like to know when either preemption and/or interrupts are disabled. + +The following code: + + local_irq_disable(); + call_function_with_irqs_off(); + preempt_disable(); + call_function_with_irqs_and_preemption_off(); + local_irq_enable(); + call_function_with_preemption_off(); + preempt_enable(); + +The irqsoff tracer will record the total length of +call_function_with_irqs_off() and +call_function_with_irqs_and_preemption_off(). + +The preemptoff tracer will record the total length of +call_function_with_irqs_and_preemption_off() and +call_function_with_preemption_off(). + +But neither will trace the time that interrupts and/or preemption +is disabled. This total time is the time that we can not schedule. +To record this time, use the preemptirqsoff tracer. + +Again, using this trace is much like the irqsoff and preemptoff tracers. + + # echo preemptoff > /debug/tracing/current_tracer + # echo 0 > /debug/tracing/tracing_max_latency + # echo 1 > /debug/tracing/tracing_enabled + # ls -ltr + [...] + # echo 0 > /debug/tracing/tracing_enabled + # cat /debug/tracing/latency_trace +# tracer: preemptirqsoff +# +preemptirqsoff latency trace v1.1.5 on 2.6.26-rc8 +-------------------------------------------------------------------- + latency: 293 us, #3/3, CPU#0 | (M:preempt VP:0, KP:0, SP:0 HP:0 #P:2) + ----------------- + | task: ls-4860 (uid:0 nice:0 policy:0 rt_prio:0) + ----------------- + => started at: apic_timer_interrupt + => ended at: __do_softirq + +# _------=> CPU# +# / _-----=> irqs-off +# | / _----=> need-resched +# || / _---=> hardirq/softirq +# ||| / _--=> preempt-depth +# |||| / +# ||||| delay +# cmd pid ||||| time | caller +# \ / ||||| \ | / + ls-4860 0d... 0us!: trace_hardirqs_off_thunk (apic_timer_interrupt) + ls-4860 0d.s. 294us : _local_bh_enable (__do_softirq) + ls-4860 0d.s1 294us : trace_preempt_on (__do_softirq) + + +vim:ft=help + + +The trace_hardirqs_off_thunk is called from assembly on x86 when +interrupts are disabled in the assembly code. Without the function +tracing, we don't know if interrupts were enabled within the preemption +points. We do see that it started with preemption enabled. + +Here is a trace with ftrace_enabled set: + + +# tracer: preemptirqsoff +# +preemptirqsoff latency trace v1.1.5 on 2.6.26-rc8 +-------------------------------------------------------------------- + latency: 105 us, #183/183, CPU#0 | (M:preempt VP:0, KP:0, SP:0 HP:0 #P:2) + ----------------- + | task: sshd-4261 (uid:0 nice:0 policy:0 rt_prio:0) + ----------------- + => started at: write_chan + => ended at: __do_softirq + +# _------=> CPU# +# / _-----=> irqs-off +# | / _----=> need-resched +# || / _---=> hardirq/softirq +# ||| / _--=> preempt-depth +# |||| / +# ||||| delay +# cmd pid ||||| time | caller +# \ / ||||| \ | / + ls-4473 0.N.. 0us : preempt_schedule (write_chan) + ls-4473 0dN.1 1us : _spin_lock (schedule) + ls-4473 0dN.1 2us : add_preempt_count (_spin_lock) + ls-4473 0d..2 2us : put_prev_task_fair (schedule) +[...] + ls-4473 0d..2 13us : set_normalized_timespec (ktime_get_ts) + ls-4473 0d..2 13us : __switch_to (schedule) + sshd-4261 0d..2 14us : finish_task_switch (schedule) + sshd-4261 0d..2 14us : _spin_unlock_irq (finish_task_switch) + sshd-4261 0d..1 15us : add_preempt_count (_spin_lock_irqsave) + sshd-4261 0d..2 16us : _spin_unlock_irqrestore (hrtick_set) + sshd-4261 0d..2 16us : do_IRQ (common_interrupt) + sshd-4261 0d..2 17us : irq_enter (do_IRQ) + sshd-4261 0d..2 17us : idle_cpu (irq_enter) + sshd-4261 0d..2 18us : add_preempt_count (irq_enter) + sshd-4261 0d.h2 18us : idle_cpu (irq_enter) + sshd-4261 0d.h. 18us : handle_fasteoi_irq (do_IRQ) + sshd-4261 0d.h. 19us : _spin_lock (handle_fasteoi_irq) + sshd-4261 0d.h. 19us : add_preempt_count (_spin_lock) + sshd-4261 0d.h1 20us : _spin_unlock (handle_fasteoi_irq) + sshd-4261 0d.h1 20us : sub_preempt_count (_spin_unlock) +[...] + sshd-4261 0d.h1 28us : _spin_unlock (handle_fasteoi_irq) + sshd-4261 0d.h1 29us : sub_preempt_count (_spin_unlock) + sshd-4261 0d.h2 29us : irq_exit (do_IRQ) + sshd-4261 0d.h2 29us : sub_preempt_count (irq_exit) + sshd-4261 0d..3 30us : do_softirq (irq_exit) + sshd-4261 0d... 30us : __do_softirq (do_softirq) + sshd-4261 0d... 31us : __local_bh_disable (__do_softirq) + sshd-4261 0d... 31us+: add_preempt_count (__local_bh_disable) + sshd-4261 0d.s4 34us : add_preempt_count (__local_bh_disable) +[...] + sshd-4261 0d.s3 43us : sub_preempt_count (local_bh_enable_ip) + sshd-4261 0d.s4 44us : sub_preempt_count (local_bh_enable_ip) + sshd-4261 0d.s3 44us : smp_apic_timer_interrupt (apic_timer_interrupt) + sshd-4261 0d.s3 45us : irq_enter (smp_apic_timer_interrupt) + sshd-4261 0d.s3 45us : idle_cpu (irq_enter) + sshd-4261 0d.s3 46us : add_preempt_count (irq_enter) + sshd-4261 0d.H3 46us : idle_cpu (irq_enter) + sshd-4261 0d.H3 47us : hrtimer_interrupt (smp_apic_timer_interrupt) + sshd-4261 0d.H3 47us : ktime_get (hrtimer_interrupt) +[...] + sshd-4261 0d.H3 81us : tick_program_event (hrtimer_interrupt) + sshd-4261 0d.H3 82us : ktime_get (tick_program_event) + sshd-4261 0d.H3 82us : ktime_get_ts (ktime_get) + sshd-4261 0d.H3 83us : getnstimeofday (ktime_get_ts) + sshd-4261 0d.H3 83us : set_normalized_timespec (ktime_get_ts) + sshd-4261 0d.H3 84us : clockevents_program_event (tick_program_event) + sshd-4261 0d.H3 84us : lapic_next_event (clockevents_program_event) + sshd-4261 0d.H3 85us : irq_exit (smp_apic_timer_interrupt) + sshd-4261 0d.H3 85us : sub_preempt_count (irq_exit) + sshd-4261 0d.s4 86us : sub_preempt_count (irq_exit) + sshd-4261 0d.s3 86us : add_preempt_count (__local_bh_disable) +[...] + sshd-4261 0d.s1 98us : sub_preempt_count (net_rx_action) + sshd-4261 0d.s. 99us : add_preempt_count (_spin_lock_irq) + sshd-4261 0d.s1 99us+: _spin_unlock_irq (run_timer_softirq) + sshd-4261 0d.s. 104us : _local_bh_enable (__do_softirq) + sshd-4261 0d.s. 104us : sub_preempt_count (_local_bh_enable) + sshd-4261 0d.s. 105us : _local_bh_enable (__do_softirq) + sshd-4261 0d.s1 105us : trace_preempt_on (__do_softirq) + + +This is a very interesting trace. It started with the preemption of +the ls task. We see that the task had the "need_resched" bit set +with the 'N' in the trace. Interrupts are disabled in the spin_lock +and the trace started. We see that a schedule took place to run +sshd. When the interrupts were enabled we took an interrupt. +On return of the interrupt the softirq ran. We took another interrupt +while running the softirq as we see with the capital 'H'. + + +wakeup +------ + +In Real-Time environment it is very important to know the wakeup +time it takes for the highest priority task that wakes up to the +time it executes. This is also known as "schedule latency". +I stress the point that this is about RT tasks. It is also important +to know the scheduling latency of non-RT tasks, but the average +schedule latency is better for non-RT tasks. Tools like +LatencyTop is more appropriate for such measurements. + +Real-Time environments is interested in the worst case latency. +That is the longest latency it takes for something to happen, and +not the average. We can have a very fast scheduler that may only +have a large latency once in a while, but that would not work well +with Real-Time tasks. The wakeup tracer was designed to record +the worst case wakeups of RT tasks. Non-RT tasks are not recorded +because the tracer only records one worst case and tracing non-RT +tasks that are unpredictable will overwrite the worst case latency +of RT tasks. + +Since this tracer only deals with RT tasks, we will run this slightly +different than we did with the previous tracers. Instead of performing +an 'ls' we will run 'sleep 1' under 'chrt' which changes the +priority of the task. + + # echo wakeup > /debug/tracing/current_tracer + # echo 0 > /debug/tracing/tracing_max_latency + # echo 1 > /debug/tracing/tracing_enabled + # chrt -f 5 sleep 1 + # echo 0 > /debug/tracing/tracing_enabled + # cat /debug/tracing/latency_trace +# tracer: wakeup +# +wakeup latency trace v1.1.5 on 2.6.26-rc8 +-------------------------------------------------------------------- + latency: 4 us, #2/2, CPU#1 | (M:preempt VP:0, KP:0, SP:0 HP:0 #P:2) + ----------------- + | task: sleep-4901 (uid:0 nice:0 policy:1 rt_prio:5) + ----------------- + +# _------=> CPU# +# / _-----=> irqs-off +# | / _----=> need-resched +# || / _---=> hardirq/softirq +# ||| / _--=> preempt-depth +# |||| / +# ||||| delay +# cmd pid ||||| time | caller +# \ / ||||| \ | / + <idle>-0 1d.h4 0us+: try_to_wake_up (wake_up_process) + <idle>-0 1d..4 4us : schedule (cpu_idle) + + +vim:ft=help + + +Running this on an idle system we see that it only took 4 microseconds +to perform the task switch. Note, since the trace marker in the +schedule is before the actual "switch" we stop the tracing when +the recorded task is about to schedule in. This may change if +we add a new marker at the end of the scheduler. + +Notice that the recorded task is 'sleep' with the PID of 4901 and it +has an rt_prio of 5. This priority is user-space priority and not +the internal kernel priority. The policy is 1 for SCHED_FIFO and 2 +for SCHED_RR. + +Doing the same with chrt -r 5 and ftrace_enabled set. + +# tracer: wakeup +# +wakeup latency trace v1.1.5 on 2.6.26-rc8 +-------------------------------------------------------------------- + latency: 50 us, #60/60, CPU#1 | (M:preempt VP:0, KP:0, SP:0 HP:0 #P:2) + ----------------- + | task: sleep-4068 (uid:0 nice:0 policy:2 rt_prio:5) + ----------------- + +# _------=> CPU# +# / _-----=> irqs-off +# | / _----=> need-resched +# || / _---=> hardirq/softirq +# ||| / _--=> preempt-depth +# |||| / +# ||||| delay +# cmd pid ||||| time | caller +# \ / ||||| \ | / +ksoftirq-7 1d.H3 0us : try_to_wake_up (wake_up_process) +ksoftirq-7 1d.H4 1us : sub_preempt_count (marker_probe_cb) +ksoftirq-7 1d.H3 2us : check_preempt_wakeup (try_to_wake_up) +ksoftirq-7 1d.H3 3us : update_curr (check_preempt_wakeup) +ksoftirq-7 1d.H3 4us : calc_delta_mine (update_curr) +ksoftirq-7 1d.H3 5us : __resched_task (check_preempt_wakeup) +ksoftirq-7 1d.H3 6us : task_wake_up_rt (try_to_wake_up) +ksoftirq-7 1d.H3 7us : _spin_unlock_irqrestore (try_to_wake_up) +[...] +ksoftirq-7 1d.H2 17us : irq_exit (smp_apic_timer_interrupt) +ksoftirq-7 1d.H2 18us : sub_preempt_count (irq_exit) +ksoftirq-7 1d.s3 19us : sub_preempt_count (irq_exit) +ksoftirq-7 1..s2 20us : rcu_process_callbacks (__do_softirq) +[...] +ksoftirq-7 1..s2 26us : __rcu_process_callbacks (rcu_process_callbacks) +ksoftirq-7 1d.s2 27us : _local_bh_enable (__do_softirq) +ksoftirq-7 1d.s2 28us : sub_preempt_count (_local_bh_enable) +ksoftirq-7 1.N.3 29us : sub_preempt_count (ksoftirqd) +ksoftirq-7 1.N.2 30us : _cond_resched (ksoftirqd) +ksoftirq-7 1.N.2 31us : __cond_resched (_cond_resched) +ksoftirq-7 1.N.2 32us : add_preempt_count (__cond_resched) +ksoftirq-7 1.N.2 33us : schedule (__cond_resched) +ksoftirq-7 1.N.2 33us : add_preempt_count (schedule) +ksoftirq-7 1.N.3 34us : hrtick_clear (schedule) +ksoftirq-7 1dN.3 35us : _spin_lock (schedule) +ksoftirq-7 1dN.3 36us : add_preempt_count (_spin_lock) +ksoftirq-7 1d..4 37us : put_prev_task_fair (schedule) +ksoftirq-7 1d..4 38us : update_curr (put_prev_task_fair) +[...] +ksoftirq-7 1d..5 47us : _spin_trylock (tracing_record_cmdline) +ksoftirq-7 1d..5 48us : add_preempt_count (_spin_trylock) +ksoftirq-7 1d..6 49us : _spin_unlock (tracing_record_cmdline) +ksoftirq-7 1d..6 49us : sub_preempt_count (_spin_unlock) +ksoftirq-7 1d..4 50us : schedule (__cond_resched) + +The interrupt went off while running ksoftirqd. This task runs at +SCHED_OTHER. Why didn't we see the 'N' set early? This may be +a harmless bug with x86_32 and 4K stacks. The need_reched() function +that tests if we need to reschedule looks on the actual stack. +Where as the setting of the NEED_RESCHED bit happens on the +task's stack. But because we are in a hard interrupt, the test +is with the interrupts stack which has that to be false. We don't +see the 'N' until we switch back to the task's stack. + +ftrace +------ + +ftrace is not only the name of the tracing infrastructure, but it +is also a name of one of the tracers. The tracer is the function +tracer. Enabling the function tracer can be done from the +debug file system. Make sure the ftrace_enabled is set otherwise +this tracer is a nop. + + # sysctl kernel.ftrace_enabled=1 + # echo ftrace > /debug/tracing/current_tracer + # echo 1 > /debug/tracing/tracing_enabled + # usleep 1 + # echo 0 > /debug/tracing/tracing_enabled + # cat /debug/tracing/trace +# tracer: ftrace +# +# TASK-PID CPU# TIMESTAMP FUNCTION +# | | | | | + bash-4003 [00] 123.638713: finish_task_switch <-schedule + bash-4003 [00] 123.638714: _spin_unlock_irq <-finish_task_switch + bash-4003 [00] 123.638714: sub_preempt_count <-_spin_unlock_irq + bash-4003 [00] 123.638715: hrtick_set <-schedule + bash-4003 [00] 123.638715: _spin_lock_irqsave <-hrtick_set + bash-4003 [00] 123.638716: add_preempt_count <-_spin_lock_irqsave + bash-4003 [00] 123.638716: _spin_unlock_irqrestore <-hrtick_set + bash-4003 [00] 123.638717: sub_preempt_count <-_spin_unlock_irqrestore + bash-4003 [00] 123.638717: hrtick_clear <-hrtick_set + bash-4003 [00] 123.638718: sub_preempt_count <-schedule + bash-4003 [00] 123.638718: sub_preempt_count <-preempt_schedule + bash-4003 [00] 123.638719: wait_for_completion <-__stop_machine_run + bash-4003 [00] 123.638719: wait_for_common <-wait_for_completion + bash-4003 [00] 123.638720: _spin_lock_irq <-wait_for_common + bash-4003 [00] 123.638720: add_preempt_count <-_spin_lock_irq +[...] + + +Note: It is sometimes better to enable or disable tracing directly from +a program, because the buffer may be overflowed by the echo commands +before you get to the point you want to trace. It is also easier to +stop the tracing at the point that you hit the part that you are +interested in. Since the ftrace buffer is a ring buffer with the +oldest data being overwritten, usually it is sufficient to start the +tracer with an echo command but have you code stop it. Something +like the following is usually appropriate for this. + +int trace_fd; +[...] +int main(int argc, char *argv[]) { + [...] + trace_fd = open("/debug/tracing/tracing_enabled", O_WRONLY); + [...] + if (condition_hit()) { + write(trace_fd, "0", 1); + } + [...] +} + + +dynamic ftrace +-------------- + +If CONFIG_DYNAMIC_FTRACE is set, then the system will run with +virtually no overhead when function tracing is disabled. The way +this works is the mcount function call (placed at the start of +every kernel function, produced by the -pg switch in gcc), starts +of pointing to a simple return. + +When dynamic ftrace is initialized, it calls kstop_machine to make it +act like a uniprocessor so that it can freely modify code without +worrying about other processors executing that same code. At +initialization, the mcount calls are change to call a "record_ip" +function. After this, the first time a kernel function is called, +it has the calling address saved in a hash table. + +Later on the ftraced kernel thread is awoken and will again call +kstop_machine if new functions have been recorded. The ftraced thread +will change all calls to mcount to "nop". Just calling mcount +and having mcount return has shown a 10% overhead. By converting +it to a nop, there is no recordable overhead to the system. + +One special side-effect to the recording of the functions being +traced, is that we can now selectively choose which functions we +want to trace and which ones we want the mcount calls to remain as +nops. + +Two files that contain to the enabling and disabling of recorded +functions are: + + set_ftrace_filter + +and + + set_ftrace_notrace + +A list of available functions that you can add to this files is listed +in: + + available_filter_functions + + # cat /debug/tracing/available_filter_functions +put_prev_task_idle +kmem_cache_create +pick_next_task_rt +get_online_cpus +pick_next_task_fair +mutex_lock +[...] + +If I'm only interested in sys_nanosleep and hrtimer_interrupt: + + # echo sys_nanosleep hrtimer_interrupt \ + > /debug/tracing/set_ftrace_filter + # echo ftrace > /debug/tracing/current_tracer + # echo 1 > /debug/tracing/tracing_enabled + # usleep 1 + # echo 0 > /debug/tracing/tracing_enabled + # cat /debug/tracing/trace +# tracer: ftrace +# +# TASK-PID CPU# TIMESTAMP FUNCTION +# | | | | | + usleep-4134 [00] 1317.070017: hrtimer_interrupt <-smp_apic_timer_interrupt + usleep-4134 [00] 1317.070111: sys_nanosleep <-syscall_call + <idle>-0 [00] 1317.070115: hrtimer_interrupt <-smp_apic_timer_interrupt + +To see what functions are being traced, you can cat the file: + + # cat /debug/tracing/set_ftrace_filter +hrtimer_interrupt +sys_nanosleep + + +Perhaps this isn't enough. The filters also allow simple wild cards. +Only the following is currently available + + <match>* - will match functions that begins with <match> + *<match> - will match functions that end with <match> + *<match>* - will match functions that have <match> in it + +Thats all the wild cards that are allowed. + + <match>*<match> will not work. + + # echo hrtimer_* > /debug/tracing/set_ftrace_filter + +Produces: + +# tracer: ftrace +# +# TASK-PID CPU# TIMESTAMP FUNCTION +# | | | | | + bash-4003 [00] 1480.611794: hrtimer_init <-copy_process + bash-4003 [00] 1480.611941: hrtimer_start <-hrtick_set + bash-4003 [00] 1480.611956: hrtimer_cancel <-hrtick_clear + bash-4003 [00] 1480.611956: hrtimer_try_to_cancel <-hrtimer_cancel + <idle>-0 [00] 1480.612019: hrtimer_get_next_event <-get_next_timer_interrupt + <idle>-0 [00] 1480.612025: hrtimer_get_next_event <-get_next_timer_interrupt + <idle>-0 [00] 1480.612032: hrtimer_get_next_event <-get_next_timer_interrupt + <idle>-0 [00] 1480.612037: hrtimer_get_next_event <-get_next_timer_interrupt + <idle>-0 [00] 1480.612382: hrtimer_get_next_event <-get_next_timer_interrupt + + +Notice that we lost the sys_nanosleep. + + # cat /debug/tracing/set_ftrace_filter +hrtimer_run_queues +hrtimer_run_pending +hrtimer_init +hrtimer_cancel +hrtimer_try_to_cancel +hrtimer_forward +hrtimer_start +hrtimer_reprogram +hrtimer_force_reprogram +hrtimer_get_next_event +hrtimer_interrupt +hrtimer_nanosleep +hrtimer_wakeup +hrtimer_get_remaining +hrtimer_get_res +hrtimer_init_sleeper + + +This is because the '>' and '>>' act just like they do in bash. +To rewrite the filters, use '>' +To append to the filters, use '>>' + +To clear out a filter so that all functions will be recorded again. + + # echo > /debug/tracing/set_ftrace_filter + # cat /debug/tracing/set_ftrace_filter + # + +Again, now we want to append. + + # echo sys_nanosleep > /debug/tracing/set_ftrace_filter + # cat /debug/tracing/set_ftrace_filter +sys_nanosleep + # echo hrtimer_* >> /debug/tracing/set_ftrace_filter + # cat /debug/tracing/set_ftrace_filter +hrtimer_run_queues +hrtimer_run_pending +hrtimer_init +hrtimer_cancel +hrtimer_try_to_cancel +hrtimer_forward +hrtimer_start +hrtimer_reprogram +hrtimer_force_reprogram +hrtimer_get_next_event +hrtimer_interrupt +sys_nanosleep +hrtimer_nanosleep +hrtimer_wakeup +hrtimer_get_remaining +hrtimer_get_res +hrtimer_init_sleeper + + +The set_ftrace_notrace prevents those functions from being traced. + + # echo '*preempt*' '*lock*' > /debug/tracing/set_ftrace_notrace + +Produces: + +# tracer: ftrace +# +# TASK-PID CPU# TIMESTAMP FUNCTION +# | | | | | + bash-4043 [01] 115.281644: finish_task_switch <-schedule + bash-4043 [01] 115.281645: hrtick_set <-schedule + bash-4043 [01] 115.281645: hrtick_clear <-hrtick_set + bash-4043 [01] 115.281646: wait_for_completion <-__stop_machine_run + bash-4043 [01] 115.281647: wait_for_common <-wait_for_completion + bash-4043 [01] 115.281647: kthread_stop <-stop_machine_run + bash-4043 [01] 115.281648: init_waitqueue_head <-kthread_stop + bash-4043 [01] 115.281648: wake_up_process <-kthread_stop + bash-4043 [01] 115.281649: try_to_wake_up <-wake_up_process + +We can see that there's no more lock or preempt tracing. + +ftraced +------- + +As mentioned above, when dynamic ftrace is configured in, a kernel +thread wakes up once a second and checks to see if there are mcount +calls that need to be converted into nops. If there is not, then +it simply goes back to sleep. But if there is, it will call +kstop_machine to convert the calls to nops. + +There may be a case that you do not want this added latency. +Perhaps you are doing some audio recording and this activity might +cause skips in the playback. There is an interface to disable +and enable the ftraced kernel thread. + + # echo 0 > /debug/tracing/ftraced_enabled + +This will disable the calling of the kstop_machine to update the +mcount calls to nops. Remember that there's a large overhead +to calling mcount. Without this kernel thread, that overhead will +exist. + +Any write to the ftraced_enabled file will cause the kstop_machine +to run if there are recorded calls to mcount. This means that a +user can manually perform the updates when they want to by simply +echoing a '0' into the ftraced_enabled file. + +The updates are also done at the beginning of enabling a tracer +that uses ftrace function recording. + + +trace_pipe +---------- + +The trace_pipe outputs the same as trace, but the effect on the +tracing is different. Every read from trace_pipe is consumed. +This means that subsequent reads will be different. The trace +is live. + + # echo ftrace > /debug/tracing/current_tracer + # cat /debug/tracing/trace_pipe > /tmp/trace.out & +[1] 4153 + # echo 1 > /debug/tracing/tracing_enabled + # usleep 1 + # echo 0 > /debug/tracing/tracing_enabled + # cat /debug/tracing/trace +# tracer: ftrace +# +# TASK-PID CPU# TIMESTAMP FUNCTION +# | | | | | + + # + # cat /tmp/trace.out + bash-4043 [00] 41.267106: finish_task_switch <-schedule + bash-4043 [00] 41.267106: hrtick_set <-schedule + bash-4043 [00] 41.267107: hrtick_clear <-hrtick_set + bash-4043 [00] 41.267108: wait_for_completion <-__stop_machine_run + bash-4043 [00] 41.267108: wait_for_common <-wait_for_completion + bash-4043 [00] 41.267109: kthread_stop <-stop_machine_run + bash-4043 [00] 41.267109: init_waitqueue_head <-kthread_stop + bash-4043 [00] 41.267110: wake_up_process <-kthread_stop + bash-4043 [00] 41.267110: try_to_wake_up <-wake_up_process + bash-4043 [00] 41.267111: select_task_rq_rt <-try_to_wake_up + + +Note, reading the trace_pipe will block until more input is added. +By changing the tracer, trace_pipe will issue an EOF. We needed +to set the ftrace tracer _before_ cating the trace_pipe file. + + +trace entries +------------- + +Having too much or not enough data can be troublesome in diagnosing +some issue in the kernel. The file trace_entries is used to modify +the size of the internal trace buffers. The numbers listed +is the number of entries that can be recorded per CPU. To know +the full size, multiply the number of possible CPUS with the +number of entries. + + # cat /debug/tracing/trace_entries +65620 + +Note, to modify this you must have tracing fulling disabled. To do that, +echo "none" into the current_tracer. + + # echo none > /debug/tracing/current_tracer + # echo 100000 > /debug/tracing/trace_entries + # cat /debug/tracing/trace_entries +100045 + + +Notice that we echoed in 100,000 but the size is 100,045. The entries +are held by individual pages. It allocates the number of pages it takes +to fulfill the request. If more entries may fit on the last page +it will add them. + + # echo 1 > /debug/tracing/trace_entries + # cat /debug/tracing/trace_entries +85 + +This shows us that 85 entries can fit on a single page. + +The number of pages that will be allocated is a percentage of available +memory. Allocating too much will produces an error. + + # echo 1000000000000 > /debug/tracing/trace_entries +-bash: echo: write error: Cannot allocate memory + # cat /debug/tracing/trace_entries +85 + diff --git a/Documentation/i2c/writing-clients b/Documentation/i2c/writing-clients index ee75cbace28d..d4cd4126d1ad 100644 --- a/Documentation/i2c/writing-clients +++ b/Documentation/i2c/writing-clients @@ -25,12 +25,23 @@ routines, and should be zero-initialized except for fields with data you provide. A client structure holds device-specific information like the driver model device node, and its I2C address. +/* iff driver uses driver model ("new style") binding model: */ + +static struct i2c_device_id foo_idtable[] = { + { "foo", my_id_for_foo }, + { "bar", my_id_for_bar }, + { } +}; + +MODULE_DEVICE_TABLE(i2c, foo_idtable); + static struct i2c_driver foo_driver = { .driver = { .name = "foo", }, /* iff driver uses driver model ("new style") binding model: */ + .id_table = foo_ids, .probe = foo_probe, .remove = foo_remove, @@ -173,10 +184,9 @@ handle may be used during foo_probe(). If foo_probe() reports success (zero not a negative status code) it may save the handle and use it until foo_remove() returns. That binding model is used by most Linux drivers. -Drivers match devices when i2c_client.driver_name and the driver name are -the same; this approach is used in several other busses that don't have -device typing support in the hardware. The driver and module name should -match, so hotplug/coldplug mechanisms will modprobe the driver. +The probe function is called when an entry in the id_table name field +matches the device's name. It is passed the entry that was matched so +the driver knows which one in the table matched. Device Creation (Standard driver model) diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt index e07c432c731f..b52f47d588b4 100644 --- a/Documentation/kernel-parameters.txt +++ b/Documentation/kernel-parameters.txt @@ -295,7 +295,7 @@ and is between 256 and 4096 characters. It is defined in the file when initialising the APIC and IO-APIC components. apm= [APM] Advanced Power Management - See header of arch/i386/kernel/apm.c. + See header of arch/x86/kernel/apm_32.c. arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards Format: <io>,<irq>,<nodeID> @@ -638,7 +638,7 @@ and is between 256 and 4096 characters. It is defined in the file elanfreq= [X86-32] See comment before function elanfreq_setup() in - arch/i386/kernel/cpu/cpufreq/elanfreq.c. + arch/x86/kernel/cpu/cpufreq/elanfreq.c. elevator= [IOSCHED] Format: {"anticipatory" | "cfq" | "deadline" | "noop"} @@ -1679,6 +1679,10 @@ and is between 256 and 4096 characters. It is defined in the file Format: <reboot_mode>[,<reboot_mode2>[,...]] See arch/*/kernel/reboot.c or arch/*/kernel/process.c + relax_domain_level= + [KNL, SMP] Set scheduler's default relax_domain_level. + See Documentation/cpusets.txt. + reserve= [KNL,BUGS] Force the kernel to ignore some iomem area reservetop= [X86-32] diff --git a/Documentation/networking/ip-sysctl.txt b/Documentation/networking/ip-sysctl.txt index 17a6e46fbd43..17f1f91af35c 100644 --- a/Documentation/networking/ip-sysctl.txt +++ b/Documentation/networking/ip-sysctl.txt @@ -81,23 +81,23 @@ inet_peer_minttl - INTEGER Minimum time-to-live of entries. Should be enough to cover fragment time-to-live on the reassembling side. This minimum time-to-live is guaranteed if the pool size is less than inet_peer_threshold. - Measured in jiffies(1). + Measured in seconds. inet_peer_maxttl - INTEGER Maximum time-to-live of entries. Unused entries will expire after this period of time if there is no memory pressure on the pool (i.e. when the number of entries in the pool is very small). - Measured in jiffies(1). + Measured in seconds. inet_peer_gc_mintime - INTEGER Minimum interval between garbage collection passes. This interval is in effect under high memory pressure on the pool. - Measured in jiffies(1). + Measured in seconds. inet_peer_gc_maxtime - INTEGER Minimum interval between garbage collection passes. This interval is in effect under low (or absent) memory pressure on the pool. - Measured in jiffies(1). + Measured in seconds. TCP variables: @@ -794,10 +794,6 @@ tag - INTEGER Allows you to write a number, which can be used as required. Default value is 0. -(1) Jiffie: internal timeunit for the kernel. On the i386 1/100s, on the -Alpha 1/1024s. See the HZ define in /usr/include/asm/param.h for the exact -value on your system. - Alexey Kuznetsov. kuznet@ms2.inr.ac.ru diff --git a/Documentation/networking/s2io.txt b/Documentation/networking/s2io.txt index 4bde53e85f3f..1e28e2ddb90a 100644 --- a/Documentation/networking/s2io.txt +++ b/Documentation/networking/s2io.txt @@ -83,9 +83,9 @@ Valid range: Limited by memory on system Default: 30 e. intr_type -Specifies interrupt type. Possible values 1(INTA), 2(MSI), 3(MSI-X) -Valid range: 1-3 -Default: 1 +Specifies interrupt type. Possible values 0(INTA), 2(MSI-X) +Valid values: 0, 2 +Default: 2 5. Performance suggestions General: diff --git a/Documentation/video4linux/CARDLIST.au0828 b/Documentation/video4linux/CARDLIST.au0828 index aaae360312e4..86d1c8e7b18f 100644 --- a/Documentation/video4linux/CARDLIST.au0828 +++ b/Documentation/video4linux/CARDLIST.au0828 @@ -1,4 +1,4 @@ 0 -> Unknown board (au0828) - 1 -> Hauppauge HVR950Q (au0828) [2040:7200] + 1 -> Hauppauge HVR950Q (au0828) [2040:7200,2040:7210,2040:7217,2040:721b,2040:721f,2040:7280,0fd9:0008] 2 -> Hauppauge HVR850 (au0828) [2040:7240] 3 -> DViCO FusionHDTV USB (au0828) [0fe9:d620] diff --git a/Documentation/vm/slabinfo.c b/Documentation/vm/slabinfo.c index e4230ed16ee7..df3227605d59 100644 --- a/Documentation/vm/slabinfo.c +++ b/Documentation/vm/slabinfo.c @@ -1,7 +1,7 @@ /* * Slabinfo: Tool to get reports about slabs * - * (C) 2007 sgi, Christoph Lameter <clameter@sgi.com> + * (C) 2007 sgi, Christoph Lameter * * Compile by: * @@ -99,7 +99,7 @@ void fatal(const char *x, ...) void usage(void) { - printf("slabinfo 5/7/2007. (c) 2007 sgi. clameter@sgi.com\n\n" + printf("slabinfo 5/7/2007. (c) 2007 sgi.\n\n" "slabinfo [-ahnpvtsz] [-d debugopts] [slab-regexp]\n" "-a|--aliases Show aliases\n" "-A|--activity Most active slabs first\n" diff --git a/Documentation/vm/slub.txt b/Documentation/vm/slub.txt index 7c13f22a0c9e..bb1f5c6e28b3 100644 --- a/Documentation/vm/slub.txt +++ b/Documentation/vm/slub.txt @@ -266,4 +266,4 @@ of other objects. slub_debug=FZ,dentry -Christoph Lameter, <clameter@sgi.com>, May 30, 2007 +Christoph Lameter, May 30, 2007 |