linux.git/kernel/sched/cpuacct.c, branch v6.12.80

Merge branch 'sched/fast-headers' into sched/core

2022-03-15T08:05:05+00:00

Merge the scheduler build speedup of the fast-headers tree.

Cumulative scheduler (kernel/sched/) build time speedup on a
Linux distribution's config, which enables all scheduler features,
compared to the vanilla kernel:

      _____________________________________________________________________________
     |
     |  Vanilla kernel (v5.13-rc7):
     |_____________________________________________________________________________
     |
     |  Performance counter stats for 'make -j96 kernel/sched/' (3 runs):
     |
     |   126,975,564,374      instructions              #    1.45  insn per cycle           ( +-  0.00% )
     |    87,637,847,671      cycles                    #    3.959 GHz                      ( +-  0.30% )
     |         22,136.96 msec cpu-clock                 #    7.499 CPUs utilized            ( +-  0.29% )
     |
     |            2.9520 +- 0.0169 seconds time elapsed  ( +-  0.57% )
     |_____________________________________________________________________________
     |
     |  Patched kernel:
     |_____________________________________________________________________________
     |
     | Performance counter stats for 'make -j96 kernel/sched/' (3 runs):
     |
     |    50,420,496,914      instructions              #    1.47  insn per cycle           ( +-  0.00% )
     |    34,234,322,038      cycles                    #    3.946 GHz                      ( +-  0.31% )
     |          8,675.81 msec cpu-clock                 #    3.053 CPUs utilized            ( +-  0.45% )
     |
     |            2.8420 +- 0.0181 seconds time elapsed  ( +-  0.64% )
     |_____________________________________________________________________________

    Summary:

      - CPU time used to build the scheduler dropped by -60.9%, a reduction
        from 22.1 clock-seconds to 8.7 clock-seconds.

      - Wall-clock time to build the scheduler dropped by -3.9%, a reduction
        from 2.95 seconds to 2.84 seconds.

Signed-off-by: Ingo Molnar

sched/cpuacct: Remove redundant RCU read lock

2022-03-01T15:18:38+00:00

The cpuacct_account_field() and it's cgroup v2 wrapper
cgroup_account_cputime_field() is only called from cputime
in task_group_account_field(), which is already in RCU read-side
critical section. So remove these redundant RCU read lock.

Suggested-by: Tejun Heo 
Signed-off-by: Chengming Zhou 
Signed-off-by: Peter Zijlstra (Intel) 
Link: https://lore.kernel.org/r/20220220051426.5274-3-zhouchengming@bytedance.com

sched/cpuacct: Optimize away RCU read lock

2022-03-01T15:18:38+00:00

Since cpuacct_charge() is called from the scheduler update_curr(),
we must already have rq lock held, then the RCU read lock can
be optimized away.

And do the same thing in it's wrapper cgroup_account_cputime(),
but we can't use lockdep_assert_rq_held() there, which defined
in kernel/sched/sched.h.

Suggested-by: Peter Zijlstra (Intel) 
Signed-off-by: Chengming Zhou 
Signed-off-by: Peter Zijlstra (Intel) 
Link: https://lore.kernel.org/r/20220220051426.5274-2-zhouchengming@bytedance.com

sched/cpuacct: Fix charge percpu cpuusage

2022-03-01T15:18:37+00:00

The cpuacct_account_field() is always called by the current task
itself, so it's ok to use __this_cpu_add() to charge the tick time.

But cpuacct_charge() maybe called by update_curr() in load_balance()
on a random CPU, different from the CPU on which the task is running.
So __this_cpu_add() will charge that cputime to a random incorrect CPU.

Fixes: 73e6aafd9ea8 ("sched/cpuacct: Simplify the cpuacct code")
Reported-by: Minye Zhu 
Signed-off-by: Chengming Zhou 
Signed-off-by: Peter Zijlstra (Intel) 
Acked-by: Tejun Heo 
Link: https://lore.kernel.org/r/20220220051426.5274-1-zhouchengming@bytedance.com

sched/headers: Introduce kernel/sched/build_utility.c and build multiple .c files there

2022-02-23T09:58:33+00:00

Collect all utility functionality source code files into a single kernel/sched/build_utility.c file,
via #include-ing the .c files:

    kernel/sched/clock.c
    kernel/sched/completion.c
    kernel/sched/loadavg.c
    kernel/sched/swait.c
    kernel/sched/wait_bit.c
    kernel/sched/wait.c

CONFIG_CPU_FREQ:
    kernel/sched/cpufreq.c

CONFIG_CPU_FREQ_GOV_SCHEDUTIL:
    kernel/sched/cpufreq_schedutil.c

CONFIG_CGROUP_CPUACCT:
    kernel/sched/cpuacct.c

CONFIG_SCHED_DEBUG:
    kernel/sched/debug.c

CONFIG_SCHEDSTATS:
    kernel/sched/stats.c

CONFIG_SMP:
   kernel/sched/cpupri.c
   kernel/sched/stop_task.c
   kernel/sched/topology.c

CONFIG_SCHED_CORE:
   kernel/sched/core_sched.c

CONFIG_PSI:
   kernel/sched/psi.c

CONFIG_MEMBARRIER:
   kernel/sched/membarrier.c

CONFIG_CPU_ISOLATION:
   kernel/sched/isolation.c

CONFIG_SCHED_AUTOGROUP:
   kernel/sched/autogroup.c

The goal is to amortize the 60+ KLOC header bloat from over a dozen build units into
a single build unit.

The build time of build_utility.c also roughly matches the build time of core.c and
fair.c - allowing better load-balancing of scheduler-only rebuilds.

Signed-off-by: Ingo Molnar 
Reviewed-by: Peter Zijlstra

sched/cpuacct: Make user/system times in cpuacct.stat more precise

2021-11-23T08:55:22+00:00

cpuacct.stat shows user time based on raw random precision tick
based counters. Use cputime_addjust() to scale these values against the
total runtime accounted by the scheduler, like we already do
for user/system times in /proc//stat.

Signed-off-by: Andrey Ryabinin 
Signed-off-by: Peter Zijlstra (Intel) 
Reviewed-by: Daniel Jordan 
Acked-by: Tejun Heo 
Link: https://lore.kernel.org/r/20211115164607.23784-4-arbn@yandex-team.com

sched/cpuacct: Fix user/system in shown cpuacct.usage*

2021-11-23T08:55:22+00:00

cpuacct has 2 different ways of accounting and showing user
and system times.

The first one uses cpuacct_account_field() to account times
and cpuacct.stat file to expose them. And this one seems to work ok.

The second one is uses cpuacct_charge() function for accounting and
set of cpuacct.usage* files to show times. Despite some attempts to
fix it in the past it still doesn't work. Sometimes while running KVM
guest the cpuacct_charge() accounts most of the guest time as
system time. This doesn't match with user&system times shown in
cpuacct.stat or proc//stat.

Demonstration:
 # git clone https://github.com/aryabinin/kvmsample
 # make
 # mkdir /sys/fs/cgroup/cpuacct/test
 # echo $$ > /sys/fs/cgroup/cpuacct/test/tasks
 # ./kvmsample &
 # for i in {1..5}; do cat /sys/fs/cgroup/cpuacct/test/cpuacct.usage_sys; sleep 1; done
 1976535645
 2979839428
 3979832704
 4983603153
 5983604157

Use cpustats accounted in cpuacct_account_field() as the source
of user/sys times for cpuacct.usage* files. Make cpuacct_charge()
to account only summary execution time.

Fixes: d740037fac70 ("sched/cpuacct: Split usage accounting into user_usage and sys_usage")
Signed-off-by: Andrey Ryabinin 
Signed-off-by: Peter Zijlstra (Intel) 
Reviewed-by: Daniel Jordan 
Acked-by: Tejun Heo 
Cc: 
Link: https://lore.kernel.org/r/20211115164607.23784-3-arbn@yandex-team.com

cpuacct: Convert BUG_ON() to WARN_ON_ONCE()

2021-11-23T08:55:22+00:00

Replace fatal BUG_ON() with more safe WARN_ON_ONCE() in cpuacct_cpuusage_read().

Signed-off-by: Andrey Ryabinin 
Signed-off-by: Peter Zijlstra (Intel) 
Reviewed-by: Daniel Jordan 
Acked-by: Tejun Heo 
Link: https://lore.kernel.org/r/20211115164607.23784-2-arbn@yandex-team.com

sched: Wrap rq::lock access

2021-05-12T09:43:26+00:00

In preparation of playing games with rq->lock, abstract the thing
using an accessor.

Signed-off-by: Peter Zijlstra (Intel) 
Tested-by: Don Hiatt 
Tested-by: Hongyu Ning 
Tested-by: Vincent Guittot 
Link: https://lkml.kernel.org/r/20210422123308.136465446@infradead.org

sched: Fix various typos

2021-03-21T23:11:52+00:00

Fix ~42 single-word typos in scheduler code comments.

We have accumulated a few fun ones over the years. :-)

Signed-off-by: Ingo Molnar 
Cc: Peter Zijlstra 
Cc: Mike Galbraith 
Cc: Juri Lelli 
Cc: Vincent Guittot 
Cc: Dietmar Eggemann 
Cc: Steven Rostedt 
Cc: Ben Segall 
Cc: Mel Gorman 
Cc: linux-kernel@vger.kernel.org