path: root/Documentation
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authorLinus Torvalds <torvalds@linux-foundation.org>2014-12-13 13:00:36 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2014-12-13 13:00:36 -0800
commit78a45c6f067824cf5d0a9fedea7339ac2e28603c (patch)
treeb4f78c8b6b9059ddace0a18c11629b8d2045f793 /Documentation
parentMerge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net (diff)
parentcgroups: Documentation: fix trivial typos and wrong paragraph numberings (diff)
Merge branch 'akpm' (second patch-bomb from Andrew)
Merge second patchbomb from Andrew Morton: - the rest of MM - misc fs fixes - add execveat() syscall - new ratelimit feature for fault-injection - decompressor updates - ipc/ updates - fallocate feature creep - fsnotify cleanups - a few other misc things * emailed patches from Andrew Morton <akpm@linux-foundation.org>: (99 commits) cgroups: Documentation: fix trivial typos and wrong paragraph numberings parisc: percpu: update comments referring to __get_cpu_var percpu: update local_ops.txt to reflect this_cpu operations percpu: remove __get_cpu_var and __raw_get_cpu_var macros fsnotify: remove destroy_list from fsnotify_mark fsnotify: unify inode and mount marks handling fallocate: create FAN_MODIFY and IN_MODIFY events mm/cma: make kmemleak ignore CMA regions slub: fix cpuset check in get_any_partial slab: fix cpuset check in fallback_alloc shmdt: use i_size_read() instead of ->i_size ipc/shm.c: fix overly aggressive shmdt() when calls span multiple segments ipc/msg: increase MSGMNI, remove scaling ipc/sem.c: increase SEMMSL, SEMMNI, SEMOPM ipc/sem.c: change memory barrier in sem_lock() to smp_rmb() lib/decompress.c: consistency of compress formats for kernel image decompress_bunzip2: off by one in get_next_block() usr/Kconfig: make initrd compression algorithm selection not expert fault-inject: add ratelimit option ratelimit: add initialization macro ...
Diffstat (limited to 'Documentation')
6 files changed, 119 insertions, 18 deletions
diff --git a/Documentation/cgroups/cpusets.txt b/Documentation/cgroups/cpusets.txt
index 3c94ff3f9693..f2235a162529 100644
--- a/Documentation/cgroups/cpusets.txt
+++ b/Documentation/cgroups/cpusets.txt
@@ -445,7 +445,7 @@ across partially overlapping sets of CPUs would risk unstable dynamics
that would be beyond our understanding. So if each of two partially
overlapping cpusets enables the flag 'cpuset.sched_load_balance', then we
form a single sched domain that is a superset of both. We won't move
-a task to a CPU outside it cpuset, but the scheduler load balancing
+a task to a CPU outside its cpuset, but the scheduler load balancing
code might waste some compute cycles considering that possibility.
This mismatch is why there is not a simple one-to-one relation
@@ -552,8 +552,8 @@ otherwise initial value -1 that indicates the cpuset has no request.
1 : search siblings (hyperthreads in a core).
2 : search cores in a package.
3 : search cpus in a node [= system wide on non-NUMA system]
- ( 4 : search nodes in a chunk of node [on NUMA system] )
- ( 5 : search system wide [on NUMA system] )
+ 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.
diff --git a/Documentation/cgroups/memory.txt b/Documentation/cgroups/memory.txt
index 46b2b5080317..a22df3ad35ff 100644
--- a/Documentation/cgroups/memory.txt
+++ b/Documentation/cgroups/memory.txt
@@ -326,7 +326,7 @@ per cgroup, instead of globally.
* tcp memory pressure: sockets memory pressure for the tcp protocol.
-2.7.3 Common use cases
+2.7.2 Common use cases
Because the "kmem" counter is fed to the main user counter, kernel memory can
never be limited completely independently of user memory. Say "U" is the user
@@ -354,19 +354,19 @@ set:
3. User Interface
-0. Configuration
+3.0. Configuration
c. Enable CONFIG_MEMCG_SWAP (to use swap extension)
d. Enable CONFIG_MEMCG_KMEM (to use kmem extension)
-1. Prepare the cgroups (see cgroups.txt, Why are cgroups needed?)
+3.1. Prepare the cgroups (see cgroups.txt, Why are cgroups needed?)
# mount -t tmpfs none /sys/fs/cgroup
# mkdir /sys/fs/cgroup/memory
# mount -t cgroup none /sys/fs/cgroup/memory -o memory
-2. Make the new group and move bash into it
+3.2. Make the new group and move bash into it
# mkdir /sys/fs/cgroup/memory/0
# echo $$ > /sys/fs/cgroup/memory/0/tasks
diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 43ecdcd39df2..4a337daf0c09 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -829,6 +829,15 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
CONFIG_DEBUG_PAGEALLOC, hence this option will not help
tracking down these problems.
+ debug_pagealloc=
+ [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
+ parameter enables the feature at boot time. In
+ default, it is disabled. We can avoid allocating huge
+ chunk of memory for debug pagealloc if we don't enable
+ it at boot time and the system will work mostly same
+ with the kernel built without CONFIG_DEBUG_PAGEALLOC.
+ on: enable the feature
debugpat [X86] Enable PAT debugging
decnet.addr= [HW,NET]
@@ -1228,9 +1237,7 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
multiple times interleaved with hugepages= to reserve
huge pages of different sizes. Valid pages sizes on
x86-64 are 2M (when the CPU supports "pse") and 1G
- (when the CPU supports the "pdpe1gb" cpuinfo flag)
- Note that 1GB pages can only be allocated at boot time
- using hugepages= and not freed afterwards.
+ (when the CPU supports the "pdpe1gb" cpuinfo flag).
hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
terminal devices. Valid values: 0..8
@@ -2506,6 +2513,12 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
See Documentation/sound/oss/oss-parameters.txt
+ page_owner= [KNL] Boot-time page_owner enabling option.
+ Storage of the information about who allocated
+ each page is disabled in default. With this switch,
+ we can turn it on.
+ on: enable the feature
panic= [KNL] Kernel behaviour on panic: delay <timeout>
timeout > 0: seconds before rebooting
timeout = 0: wait forever
diff --git a/Documentation/local_ops.txt b/Documentation/local_ops.txt
index 300da4bdfdbd..407576a23317 100644
--- a/Documentation/local_ops.txt
+++ b/Documentation/local_ops.txt
@@ -8,6 +8,11 @@ to implement them for any given architecture and shows how they can be used
properly. It also stresses on the precautions that must be taken when reading
those local variables across CPUs when the order of memory writes matters.
+Note that local_t based operations are not recommended for general kernel use.
+Please use the this_cpu operations instead unless there is really a special purpose.
+Most uses of local_t in the kernel have been replaced by this_cpu operations.
+this_cpu operations combine the relocation with the local_t like semantics in
+a single instruction and yield more compact and faster executing code.
* Purpose of local atomic operations
@@ -87,10 +92,10 @@ the per cpu variable. For instance :
-If you are already in a preemption-safe context, you can directly use
-__get_cpu_var() instead.
+If you are already in a preemption-safe context, you can use
+this_cpu_ptr() instead.
- local_inc(&__get_cpu_var(counters));
+ local_inc(this_cpu_ptr(&counters));
@@ -134,7 +139,7 @@ static void test_each(void *info)
/* Increment the counter from a non preemptible context */
printk("Increment on cpu %d\n", smp_processor_id());
- local_inc(&__get_cpu_var(counters));
+ local_inc(this_cpu_ptr(&counters));
/* This is what incrementing the variable would look like within a
* preemptible context (it disables preemption) :
diff --git a/Documentation/sysctl/kernel.txt b/Documentation/sysctl/kernel.txt
index b5d0c8501a18..75511efefc64 100644
--- a/Documentation/sysctl/kernel.txt
+++ b/Documentation/sysctl/kernel.txt
@@ -116,10 +116,12 @@ set during run time.
-Enables/Disables automatic recomputing of msgmni upon memory add/remove
-or upon ipc namespace creation/removal (see the msgmni description
-above). Echoing "1" into this file enables msgmni automatic recomputing.
-Echoing "0" turns it off. auto_msgmni default value is 1.
+This variable has no effect and may be removed in future kernel
+releases. Reading it always returns 0.
+Up to Linux 3.17, it enabled/disabled automatic recomputing of msgmni
+upon memory add/remove or upon ipc namespace creation/removal.
+Echoing "1" into this file enabled msgmni automatic recomputing.
+Echoing "0" turned it off. auto_msgmni default value was 1.
diff --git a/Documentation/vm/page_owner.txt b/Documentation/vm/page_owner.txt
new file mode 100644
index 000000000000..8f3ce9b3aa11
--- /dev/null
+++ b/Documentation/vm/page_owner.txt
@@ -0,0 +1,81 @@
+page owner: Tracking about who allocated each page
+* Introduction
+page owner is for the tracking about who allocated each page.
+It can be used to debug memory leak or to find a memory hogger.
+When allocation happens, information about allocation such as call stack
+and order of pages is stored into certain storage for each page.
+When we need to know about status of all pages, we can get and analyze
+this information.
+Although we already have tracepoint for tracing page allocation/free,
+using it for analyzing who allocate each page is rather complex. We need
+to enlarge the trace buffer for preventing overlapping until userspace
+program launched. And, launched program continually dump out the trace
+buffer for later analysis and it would change system behviour with more
+possibility rather than just keeping it in memory, so bad for debugging.
+page owner can also be used for various purposes. For example, accurate
+fragmentation statistics can be obtained through gfp flag information of
+each page. It is already implemented and activated if page owner is
+enabled. Other usages are more than welcome.
+page owner is disabled in default. So, if you'd like to use it, you need
+to add "page_owner=on" into your boot cmdline. If the kernel is built
+with page owner and page owner is disabled in runtime due to no enabling
+boot option, runtime overhead is marginal. If disabled in runtime, it
+doesn't require memory to store owner information, so there is no runtime
+memory overhead. And, page owner inserts just two unlikely branches into
+the page allocator hotpath and if it returns false then allocation is
+done like as the kernel without page owner. These two unlikely branches
+would not affect to allocation performance. Following is the kernel's
+code size change due to this facility.
+- Without page owner
+ text data bss dec hex filename
+ 40662 1493 644 42799 a72f mm/page_alloc.o
+- With page owner
+ text data bss dec hex filename
+ 40892 1493 644 43029 a815 mm/page_alloc.o
+ 1427 24 8 1459 5b3 mm/page_ext.o
+ 2722 50 0 2772 ad4 mm/page_owner.o
+Although, roughly, 4 KB code is added in total, page_alloc.o increase by
+230 bytes and only half of it is in hotpath. Building the kernel with
+page owner and turning it on if needed would be great option to debug
+kernel memory problem.
+There is one notice that is caused by implementation detail. page owner
+stores information into the memory from struct page extension. This memory
+is initialized some time later than that page allocator starts in sparse
+memory system, so, until initialization, many pages can be allocated and
+they would have no owner information. To fix it up, these early allocated
+pages are investigated and marked as allocated in initialization phase.
+Although it doesn't mean that they have the right owner information,
+at least, we can tell whether the page is allocated or not,
+more accurately. On 2GB memory x86-64 VM box, 13343 early allocated pages
+are catched and marked, although they are mostly allocated from struct
+page extension feature. Anyway, after that, no page is left in
+un-tracking state.
+* Usage
+1) Build user-space helper
+ cd tools/vm
+ make page_owner_sort
+2) Enable page owner
+ Add "page_owner=on" to boot cmdline.
+3) Do the job what you want to debug
+4) Analyze information from page owner
+ cat /sys/kernel/debug/page_owner > page_owner_full.txt
+ grep -v ^PFN page_owner_full.txt > page_owner.txt
+ ./page_owner_sort page_owner.txt sorted_page_owner.txt
+ See the result about who allocated each page
+ in the sorted_page_owner.txt.