linux-stable.git/kernel/sched/cputime.c, branch linux-4.15.y

Merge branch 'for-4.15' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup

2017-11-15T22:29:44+00:00

Pull cgroup updates from Tejun Heo:
 "Cgroup2 cpu controller support is finally merged.

   - Basic cpu statistics support to allow monitoring by default without
     the CPU controller enabled.

   - cgroup2 cpu controller support.

   - /sys/kernel/cgroup files to help dealing with new / optional
     features"

* 'for-4.15' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup:
  cgroup: export list of cgroups v2 features using sysfs
  cgroup: export list of delegatable control files using sysfs
  cgroup: mark @cgrp __maybe_unused in cpu_stat_show()
  MAINTAINERS: relocate cpuset.c
  cgroup, sched: Move basic cpu stats from cgroup.stat to cpu.stat
  sched: Implement interface for cgroup unified hierarchy
  sched: Misc preps for cgroup unified hierarchy interface
  sched/cputime: Add dummy cputime_adjust() implementation for CONFIG_VIRT_CPU_ACCOUNTING_NATIVE
  cgroup: statically initialize init_css_set->dfl_cgrp
  cgroup: Implement cgroup2 basic CPU usage accounting
  cpuacct: Introduce cgroup_account_cputime[_field]()
  sched/cputime: Expose cputime_adjust()

sched/clock, sched/cputime: Use lockdep to assert IRQs are disabled/enabled

2017-11-08T10:13:53+00:00

Use lockdep to check that IRQs are enabled or disabled as expected. This
way the sanity check only shows overhead when concurrency correctness
debug code is enabled.

Signed-off-by: Frederic Weisbecker 
Acked-by: Thomas Gleixner 
Cc: David S . Miller 
Cc: Lai Jiangshan 
Cc: Linus Torvalds 
Cc: Paul E. McKenney 
Cc: Peter Zijlstra 
Cc: Tejun Heo 
Link: http://lkml.kernel.org/r/1509980490-4285-12-git-send-email-frederic@kernel.org
Signed-off-by: Ingo Molnar

sched/cputime: Add dummy cputime_adjust() implementation for CONFIG_VIRT_CPU_ACCOUNTING_NATIVE

2017-09-25T21:27:54+00:00

cfb766da54d9 ("sched/cputime: Expose cputime_adjust()") made
cputime_adjust() public for cgroup basic cpu stat support; however,
the commit forgot to add a dummy implementaiton for
CONFIG_VIRT_CPU_ACCOUNTING_NATIVE leading to compiler errors on some
s390 configurations.

Fix it by adding the missing dummy implementation.

Reported-by: “kbuild-all@01.org” 
Fixes: cfb766da54d9 ("sched/cputime: Expose cputime_adjust()")
Signed-off-by: Tejun Heo

cpuacct: Introduce cgroup_account_cputime[_field]()

2017-09-25T15:12:04+00:00

Introduce cgroup_account_cputime[_field]() which wrap cpuacct_charge()
and cgroup_account_field().  This doesn't introduce any functional
changes and will be used to add cgroup basic resource accounting.

Signed-off-by: Tejun Heo 
Acked-by: Peter Zijlstra 
Cc: Ingo Molnar

sched/cputime: Expose cputime_adjust()

2017-09-25T15:12:04+00:00

Will be used by basic cgroup resource stat reporting later.

Signed-off-by: Tejun Heo 
Acked-by: Peter Zijlstra 
Cc: Ingo Molnar 
Cc: Li Zefan 
Cc: Johannes Weiner

sched/cputime: Don't use smp_processor_id() in preemptible context

2017-07-14T08:27:15+00:00

Recent kernels trigger this warning:

 BUG: using smp_processor_id() in preemptible [00000000] code: 99-trinity/181
 caller is debug_smp_processor_id+0x17/0x19
 CPU: 0 PID: 181 Comm: 99-trinity Not tainted 4.12.0-01059-g2a42eb9 #1
 Call Trace:
  dump_stack+0x82/0xb8
  check_preemption_disabled()
  debug_smp_processor_id()
  vtime_delta()
  task_cputime()
  thread_group_cputime()
  thread_group_cputime_adjusted()
  wait_consider_task()
  do_wait()
  SYSC_wait4()
  do_syscall_64()
  entry_SYSCALL64_slow_path()

As Frederic pointed out:

| Although those sched_clock_cpu() things seem to only matter when the
| sched_clock() is unstable. And that stability is a condition for nohz_full
| to work anyway. So probably sched_clock() alone would be enough.

This patch fixes it by replacing sched_clock_cpu() with sched_clock() to
avoid calling smp_processor_id() in a preemptible context.

Reported-by: Xiaolong Ye 
Signed-off-by: Wanpeng Li 
Cc: Frederic Weisbecker 
Cc: Linus Torvalds 
Cc: Luiz Capitulino 
Cc: Peter Zijlstra 
Cc: Rik van Riel 
Cc: Thomas Gleixner 
Link: http://lkml.kernel.org/r/1499586028-7402-1-git-send-email-wanpeng.li@hotmail.com
[ Prettified the changelog. ]
Signed-off-by: Ingo Molnar

sched/cputime: Accumulate vtime on top of nsec clocksource

2017-07-05T07:54:15+00:00

Currently the cputime source used by vtime is jiffies. When we cross
a context boundary and jiffies have changed since the last snapshot, the
pending cputime is accounted to the switching out context.

This system works ok if the ticks are not aligned across CPUs. If they
instead are aligned (ie: all fire at the same time) and the CPUs run in
userspace, the jiffies change is only observed on tick exit and therefore
the user cputime is accounted as system cputime. This is because the
CPU that maintains timekeeping fires its tick at the same time as the
others. It updates jiffies in the middle of the tick and the other CPUs
see that update on IRQ exit:

    CPU 0 (timekeeper)                  CPU 1
    -------------------              -------------
                      jiffies = N
    ...                              run in userspace for a jiffy
    tick entry                       tick entry (sees jiffies = N)
    set jiffies = N + 1
    tick exit                        tick exit (sees jiffies = N + 1)
                                                account 1 jiffy as stime

Fix this with using a nanosec clock source instead of jiffies. The
cputime is then accumulated and flushed everytime the pending delta
reaches a jiffy in order to mitigate the accounting overhead.

[ fweisbec: changelog, rebase on struct vtime, field renames, add delta
  on cputime readers, keep idle vtime as-is (low overhead accounting),
  harmonize clock sources. ]

Suggested-by: Thomas Gleixner 
Reported-by: Luiz Capitulino 
Tested-by: Luiz Capitulino 
Signed-off-by: Wanpeng Li 
Signed-off-by: Frederic Weisbecker 
Reviewed-by: Thomas Gleixner 
Acked-by: Rik van Riel 
Cc: Linus Torvalds 
Cc: Peter Zijlstra 
Cc: Wanpeng Li 
Link: http://lkml.kernel.org/r/1498756511-11714-6-git-send-email-fweisbec@gmail.com
Signed-off-by: Ingo Molnar

sched/cputime: Move the vtime task fields to their own struct

2017-07-05T07:54:15+00:00

We are about to add vtime accumulation fields to the task struct. Let's
avoid more bloatification and gather vtime information to their own
struct.

Tested-by: Luiz Capitulino 
Signed-off-by: Frederic Weisbecker 
Reviewed-by: Thomas Gleixner 
Acked-by: Rik van Riel 
Cc: Linus Torvalds 
Cc: Peter Zijlstra 
Cc: Wanpeng Li 
Link: http://lkml.kernel.org/r/1498756511-11714-5-git-send-email-fweisbec@gmail.com
Signed-off-by: Ingo Molnar

sched/cputime: Rename vtime fields

2017-07-05T07:54:14+00:00

The current "snapshot" based naming on vtime fields suggests we record
some past event but that's a low level picture of their actual purpose
which comes out blurry. The real point of these fields is to run a basic
state machine that tracks down cputime entry while switching between
contexts.

So lets reflect that with more meaningful names.

Tested-by: Luiz Capitulino 
Signed-off-by: Frederic Weisbecker 
Reviewed-by: Thomas Gleixner 
Acked-by: Rik van Riel 
Cc: Linus Torvalds 
Cc: Peter Zijlstra 
Cc: Wanpeng Li 
Link: http://lkml.kernel.org/r/1498756511-11714-4-git-send-email-fweisbec@gmail.com
Signed-off-by: Ingo Molnar

sched/cputime: Always set tsk->vtime_snap_whence after accounting vtime

2017-07-05T07:54:14+00:00

Even though it doesn't have functional consequences, setting
the task's new context state after we actually accounted the pending
vtime from the old context state makes more sense from a review
perspective.

vtime_user_exit() is the only function that doesn't follow that rule
and that can bug the reviewer for a little while until he realizes there
is no reason for this special case.

Tested-by: Luiz Capitulino 
Signed-off-by: Frederic Weisbecker 
Reviewed-by: Thomas Gleixner 
Acked-by: Rik van Riel 
Cc: Linus Torvalds 
Cc: Peter Zijlstra 
Cc: Wanpeng Li 
Link: http://lkml.kernel.org/r/1498756511-11714-3-git-send-email-fweisbec@gmail.com
Signed-off-by: Ingo Molnar