diff options
| author | Frederic Weisbecker <fweisbec@gmail.com> | 2017-04-25 16:10:48 +0200 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2017-04-27 09:08:26 +0200 |
| commit | 25e2d8c1b9e327ed260edd13169cc22bc7a78bc6 (patch) | |
| tree | 5b3188a9ed2b656c729820daab75993bb4d73363 /kernel/sched/sched.h | |
| parent | ea839b41744dffe5c77b8d9842c9bb7073460901 (diff) | |
| download | linux-25e2d8c1b9e327ed260edd13169cc22bc7a78bc6.tar.bz2 | |
sched/cputime: Fix ksoftirqd cputime accounting regression
irq_time_read() returns the irqtime minus the ksoftirqd time. This
is necessary because irq_time_read() is used to substract the IRQ time
from the sum_exec_runtime of a task. If we were to include the softirq
time of ksoftirqd, this task would substract its own CPU time everytime
it updates ksoftirqd->sum_exec_runtime which would therefore never
progress.
But this behaviour got broken by:
a499a5a14db ("sched/cputime: Increment kcpustat directly on irqtime account")
... which now includes ksoftirqd softirq time in the time returned by
irq_time_read().
This has resulted in wrong ksoftirqd cputime reported to userspace
through /proc/stat and thus "top" not showing ksoftirqd when it should
after intense networking load.
ksoftirqd->stime happens to be correct but it gets scaled down by
sum_exec_runtime through task_cputime_adjusted().
To fix this, just account the strict IRQ time in a separate counter and
use it to report the IRQ time.
Reported-and-tested-by: Jesper Dangaard Brouer <brouer@redhat.com>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Reviewed-by: Rik van Riel <riel@redhat.com>
Acked-by: Jesper Dangaard Brouer <brouer@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stanislaw Gruszka <sgruszka@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Wanpeng Li <wanpeng.li@hotmail.com>
Link: http://lkml.kernel.org/r/1493129448-5356-1-git-send-email-fweisbec@gmail.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'kernel/sched/sched.h')
| -rw-r--r-- | kernel/sched/sched.h | 9 |
1 files changed, 7 insertions, 2 deletions
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h index 5cbf92214ad8..767aab3505a8 100644 --- a/kernel/sched/sched.h +++ b/kernel/sched/sched.h @@ -1869,6 +1869,7 @@ static inline void nohz_balance_exit_idle(unsigned int cpu) { } #ifdef CONFIG_IRQ_TIME_ACCOUNTING struct irqtime { + u64 total; u64 tick_delta; u64 irq_start_time; struct u64_stats_sync sync; @@ -1876,16 +1877,20 @@ struct irqtime { DECLARE_PER_CPU(struct irqtime, cpu_irqtime); +/* + * Returns the irqtime minus the softirq time computed by ksoftirqd. + * Otherwise ksoftirqd's sum_exec_runtime is substracted its own runtime + * and never move forward. + */ static inline u64 irq_time_read(int cpu) { struct irqtime *irqtime = &per_cpu(cpu_irqtime, cpu); - u64 *cpustat = kcpustat_cpu(cpu).cpustat; unsigned int seq; u64 total; do { seq = __u64_stats_fetch_begin(&irqtime->sync); - total = cpustat[CPUTIME_SOFTIRQ] + cpustat[CPUTIME_IRQ]; + total = irqtime->total; } while (__u64_stats_fetch_retry(&irqtime->sync, seq)); return total; |