wireguard-linux/kernel/sched/psi.c, branch jd/unified-crypt-queue

psi: Move PF_MEMSTALL out of task->flags

2020-03-20T12:06:19Z

The task->flags is a 32-bits flag, in which 31 bits have already been consumed. So it is hardly to introduce other new per process flag. Currently there're still enough spaces in the bit-field section of task_struct, so we can define the memstall state as a single bit in task_struct instead. This patch also removes an out-of-date comment pointed by Matthew. Suggested-by: Johannes Weiner Signed-off-by: Yafang Shao Signed-off-by: Peter Zijlstra (Intel) Acked-by: Johannes Weiner Link: https://lkml.kernel.org/r/1584408485-1921-1-git-send-email-laoar.shao@gmail.com

psi: Optimize switching tasks inside shared cgroups

2020-03-20T12:06:19Z

When switching tasks running on a CPU, the psi state of a cgroup containing both of these tasks does not change. Right now, we don't exploit that, and can perform many unnecessary state changes in nested hierarchies, especially when most activity comes from one leaf cgroup. This patch implements an optimization where we only update cgroups whose state actually changes during a task switch. These are all cgroups that contain one task but not the other, up to the first shared ancestor. When both tasks are in the same group, we don't need to update anything at all. We can identify the first shared ancestor by walking the groups of the incoming task until we see TSK_ONCPU set on the local CPU; that's the first group that also contains the outgoing task. The new psi_task_switch() is similar to psi_task_change(). To allow code reuse, move the task flag maintenance code into a new function and the poll/avg worker wakeups into the shared psi_group_change(). Suggested-by: Peter Zijlstra Signed-off-by: Johannes Weiner Signed-off-by: Peter Zijlstra (Intel) Link: https://lkml.kernel.org/r/20200316191333.115523-3-hannes@cmpxchg.org

psi: Fix cpu.pressure for cpu.max and competing cgroups

2020-03-20T12:06:18Z

For simplicity, cpu pressure is defined as having more than one runnable task on a given CPU. This works on the system-level, but it has limitations in a cgrouped reality: When cpu.max is in use, it doesn't capture the time in which a task is not executing on the CPU due to throttling. Likewise, it doesn't capture the time in which a competing cgroup is occupying the CPU - meaning it only reflects cgroup-internal competitive pressure, not outside pressure. Enable tracking of currently executing tasks, and then change the definition of cpu pressure in a cgroup from NR_RUNNING > 1 to NR_RUNNING > ON_CPU which will capture the effects of cpu.max as well as competition from outside the cgroup. After this patch, a cgroup running `stress -c 1` with a cpu.max setting of 5000 10000 shows ~50% continuous CPU pressure. Signed-off-by: Johannes Weiner Signed-off-by: Peter Zijlstra (Intel) Link: https://lkml.kernel.org/r/20200316191333.115523-2-hannes@cmpxchg.org

Merge branch 'sched-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

2020-02-15T20:51:22Z

Pull scheduler fixes from Ingo Molnar: "Misc fixes all over the place: - Fix NUMA over-balancing between lightly loaded nodes. This is fallout of the big load-balancer rewrite. - Fix the NOHZ remote loadavg update logic, which fixes anomalies like reported 150 loadavg on mostly idle CPUs. - Fix XFS performance/scalability - Fix throttled groups unbound task-execution bug - Fix PSI procfs boundary condition - Fix the cpu.uclamp.{min,max} cgroup configuration write checks - Fix DocBook annotations - Fix RCU annotations - Fix overly CPU-intensive housekeeper CPU logic loop on large CPU counts" * 'sched-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: sched/fair: Fix kernel-doc warning in attach_entity_load_avg() sched/core: Annotate curr pointer in rq with __rcu sched/psi: Fix OOB write when writing 0 bytes to PSI files sched/fair: Allow a per-CPU kthread waking a task to stack on the same CPU, to fix XFS performance regression sched/fair: Prevent unlimited runtime on throttled group sched/nohz: Optimize get_nohz_timer_target() sched/uclamp: Reject negative values in cpu_uclamp_write() sched/fair: Allow a small load imbalance between low utilisation SD_NUMA domains timers/nohz: Update NOHZ load in remote tick sched/core: Don't skip remote tick for idle CPUs

sched/psi: Fix OOB write when writing 0 bytes to PSI files

2020-02-11T12:00:02Z

Issuing write() with count parameter set to 0 on any file under /proc/pressure/ will cause an OOB write because of the access to buf[buf_size-1] when NUL-termination is performed. Fix this by checking for buf_size to be non-zero. Signed-off-by: Suren Baghdasaryan Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Ingo Molnar Acked-by: Johannes Weiner Link: https://lkml.kernel.org/r/20200203212216.7076-1-surenb@google.com

proc: convert everything to "struct proc_ops"

2020-02-04T03:05:26Z

The most notable change is DEFINE_SHOW_ATTRIBUTE macro split in seq_file.h. Conversion rule is: llseek => proc_lseek unlocked_ioctl => proc_ioctl xxx => proc_xxx delete ".owner = THIS_MODULE" line [akpm@linux-foundation.org: fix drivers/isdn/capi/kcapi_proc.c] [sfr@canb.auug.org.au: fix kernel/sched/psi.c] Link: http://lkml.kernel.org/r/20200122180545.36222f50@canb.auug.org.au Link: http://lkml.kernel.org/r/20191225172546.GB13378@avx2 Signed-off-by: Alexey Dobriyan Signed-off-by: Stephen Rothwell Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

sched/psi: create /proc/pressure and /proc/pressure/{io|memory|cpu} only when psi enabled

2020-01-17T09:19:22Z

when CONFIG_PSI_DEFAULT_DISABLED set to N or the command line set psi=0, I think we should not create /proc/pressure and /proc/pressure/{io|memory|cpu}. In the future, user maybe determine whether the psi feature is enabled by checking the existence of the /proc/pressure dir or /proc/pressure/{io|memory|cpu} files. Signed-off-by: Wang Long Signed-off-by: Peter Zijlstra (Intel) Acked-by: Johannes Weiner Link: https://lkml.kernel.org/r/1576672698-32504-1-git-send-email-w@laoqinren.net

psi: Fix a division error in psi poll()

2019-12-17T12:32:48Z

The psi window size is a u64 an can be up to 10 seconds right now, which exceeds the lower 32 bits of the variable. We currently use div_u64 for it, which is meant only for 32-bit divisors. The result is garbage pressure sampling values and even potential div0 crashes. Use div64_u64. Signed-off-by: Johannes Weiner Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Suren Baghdasaryan Cc: Jingfeng Xie Link: https://lkml.kernel.org/r/20191203183524.41378-3-hannes@cmpxchg.org

sched/psi: Fix sampling error and rare div0 crashes with cgroups and high uptime

2019-12-17T12:32:47Z

Jingfeng reports rare div0 crashes in psi on systems with some uptime: [58914.066423] divide error: 0000 [#1] SMP [58914.070416] Modules linked in: ipmi_poweroff ipmi_watchdog toa overlay fuse tcp_diag inet_diag binfmt_misc aisqos(O) aisqos_hotfixes(O) [58914.083158] CPU: 94 PID: 140364 Comm: kworker/94:2 Tainted: G W OE K 4.9.151-015.ali3000.alios7.x86_64 #1 [58914.093722] Hardware name: Alibaba Alibaba Cloud ECS/Alibaba Cloud ECS, BIOS 3.23.34 02/14/2019 [58914.102728] Workqueue: events psi_update_work [58914.107258] task: ffff8879da83c280 task.stack: ffffc90059dcc000 [58914.113336] RIP: 0010:[] [] psi_update_stats+0x1c1/0x330 [58914.122183] RSP: 0018:ffffc90059dcfd60 EFLAGS: 00010246 [58914.127650] RAX: 0000000000000000 RBX: ffff8858fe98be50 RCX: 000000007744d640 [58914.134947] RDX: 0000000000000000 RSI: 0000000000000000 RDI: 00003594f700648e [58914.142243] RBP: ffffc90059dcfdf8 R08: 0000359500000000 R09: 0000000000000000 [58914.149538] R10: 0000000000000000 R11: 0000000000000000 R12: 0000359500000000 [58914.156837] R13: 0000000000000000 R14: 0000000000000000 R15: ffff8858fe98bd78 [58914.164136] FS: 0000000000000000(0000) GS:ffff887f7f380000(0000) knlGS:0000000000000000 [58914.172529] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [58914.178467] CR2: 00007f2240452090 CR3: 0000005d5d258000 CR4: 00000000007606f0 [58914.185765] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 [58914.193061] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 [58914.200360] PKRU: 55555554 [58914.203221] Stack: [58914.205383] ffff8858fe98bd48 00000000000002f0 0000002e81036d09 ffffc90059dcfde8 [58914.213168] ffff8858fe98bec8 0000000000000000 0000000000000000 0000000000000000 [58914.220951] 0000000000000000 0000000000000000 0000000000000000 0000000000000000 [58914.228734] Call Trace: [58914.231337] [] psi_update_work+0x22/0x60 [58914.237067] [] process_one_work+0x189/0x420 [58914.243063] [] worker_thread+0x4e/0x4b0 [58914.248701] [] ? process_one_work+0x420/0x420 [58914.254869] [] kthread+0xe6/0x100 [58914.259994] [] ? kthread_park+0x60/0x60 [58914.265640] [] ret_from_fork+0x39/0x50 [58914.271193] Code: 41 29 c3 4d 39 dc 4d 0f 42 dc <49> f7 f1 48 8b 13 48 89 c7 48 c1 [58914.279691] RIP [] psi_update_stats+0x1c1/0x330 The crashing instruction is trying to divide the observed stall time by the sampling period. The period, stored in R8, is not 0, but we are dividing by the lower 32 bits only, which are all 0 in this instance. We could switch to a 64-bit division, but the period shouldn't be that big in the first place. It's the time between the last update and the next scheduled one, and so should always be around 2s and comfortably fit into 32 bits. The bug is in the initialization of new cgroups: we schedule the first sampling event in a cgroup as an offset of sched_clock(), but fail to initialize the last_update timestamp, and it defaults to 0. That results in a bogusly large sampling period the first time we run the sampling code, and consequently we underreport pressure for the first 2s of a cgroup's life. But worse, if sched_clock() is sufficiently advanced on the system, and the user gets unlucky, the period's lower 32 bits can all be 0 and the sampling division will crash. Fix this by initializing the last update timestamp to the creation time of the cgroup, thus correctly marking the start of the first pressure sampling period in a new cgroup. Reported-by: Jingfeng Xie Signed-off-by: Johannes Weiner Signed-off-by: Peter Zijlstra (Intel) Cc: Suren Baghdasaryan Link: https://lkml.kernel.org/r/20191203183524.41378-2-hannes@cmpxchg.org

Merge branch 'sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

2019-09-17T00:25:49Z

Pull scheduler updates from Ingo Molnar: - MAINTAINERS: Add Mark Rutland as perf submaintainer, Juri Lelli and Vincent Guittot as scheduler submaintainers. Add Dietmar Eggemann, Steven Rostedt, Ben Segall and Mel Gorman as scheduler reviewers. As perf and the scheduler is getting bigger and more complex, document the status quo of current responsibilities and interests, and spread the review pain^H^H^H^H fun via an increase in the Cc: linecount generated by scripts/get_maintainer.pl. :-) - Add another series of patches that brings the -rt (PREEMPT_RT) tree closer to mainline: split the monolithic CONFIG_PREEMPT dependencies into a new CONFIG_PREEMPTION category that will allow the eventual introduction of CONFIG_PREEMPT_RT. Still a few more hundred patches to go though. - Extend the CPU cgroup controller with uclamp.min and uclamp.max to allow the finer shaping of CPU bandwidth usage. - Micro-optimize energy-aware wake-ups from O(CPUS^2) to O(CPUS). - Improve the behavior of high CPU count, high thread count applications running under cpu.cfs_quota_us constraints. - Improve balancing with SCHED_IDLE (SCHED_BATCH) tasks present. - Improve CPU isolation housekeeping CPU allocation NUMA locality. - Fix deadline scheduler bandwidth calculations and logic when cpusets rebuilds the topology, or when it gets deadline-throttled while it's being offlined. - Convert the cpuset_mutex to percpu_rwsem, to allow it to be used from setscheduler() system calls without creating global serialization. Add new synchronization between cpuset topology-changing events and the deadline acceptance tests in setscheduler(), which were broken before. - Rework the active_mm state machine to be less confusing and more optimal. - Rework (simplify) the pick_next_task() slowpath. - Improve load-balancing on AMD EPYC systems. - ... and misc cleanups, smaller fixes and improvements - please see the Git log for more details. * 'sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (53 commits) sched/psi: Correct overly pessimistic size calculation sched/fair: Speed-up energy-aware wake-ups sched/uclamp: Always use 'enum uclamp_id' for clamp_id values sched/uclamp: Update CPU's refcount on TG's clamp changes sched/uclamp: Use TG's clamps to restrict TASK's clamps sched/uclamp: Propagate system defaults to the root group sched/uclamp: Propagate parent clamps sched/uclamp: Extend CPU's cgroup controller sched/topology: Improve load balancing on AMD EPYC systems arch, ia64: Make NUMA select SMP sched, perf: MAINTAINERS update, add submaintainers and reviewers sched/fair: Use rq_lock/unlock in online_fair_sched_group cpufreq: schedutil: fix equation in comment sched: Rework pick_next_task() slow-path sched: Allow put_prev_task() to drop rq->lock sched/fair: Expose newidle_balance() sched: Add task_struct pointer to sched_class::set_curr_task sched: Rework CPU hotplug task selection sched/{rt,deadline}: Fix set_next_task vs pick_next_task sched: Fix kerneldoc comment for ia64_set_curr_task ...