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authorFrederic Weisbecker <fweisbec@gmail.com>2017-04-25 16:10:48 +0200
committerIngo Molnar <mingo@kernel.org>2017-04-27 09:08:26 +0200
commit25e2d8c1b9e327ed260edd13169cc22bc7a78bc6 (patch)
tree5b3188a9ed2b656c729820daab75993bb4d73363 /kernel/sched/cputime.c
parentea839b41744dffe5c77b8d9842c9bb7073460901 (diff)
downloadlinux-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/cputime.c')
-rw-r--r--kernel/sched/cputime.c27
1 files changed, 16 insertions, 11 deletions
diff --git a/kernel/sched/cputime.c b/kernel/sched/cputime.c
index f3778e2b46c8..aea3135c5d90 100644
--- a/kernel/sched/cputime.c
+++ b/kernel/sched/cputime.c
@@ -34,6 +34,18 @@ void disable_sched_clock_irqtime(void)
sched_clock_irqtime = 0;
}
+static void irqtime_account_delta(struct irqtime *irqtime, u64 delta,
+ enum cpu_usage_stat idx)
+{
+ u64 *cpustat = kcpustat_this_cpu->cpustat;
+
+ u64_stats_update_begin(&irqtime->sync);
+ cpustat[idx] += delta;
+ irqtime->total += delta;
+ irqtime->tick_delta += delta;
+ u64_stats_update_end(&irqtime->sync);
+}
+
/*
* Called before incrementing preempt_count on {soft,}irq_enter
* and before decrementing preempt_count on {soft,}irq_exit.
@@ -41,7 +53,6 @@ void disable_sched_clock_irqtime(void)
void irqtime_account_irq(struct task_struct *curr)
{
struct irqtime *irqtime = this_cpu_ptr(&cpu_irqtime);
- u64 *cpustat = kcpustat_this_cpu->cpustat;
s64 delta;
int cpu;
@@ -52,22 +63,16 @@ void irqtime_account_irq(struct task_struct *curr)
delta = sched_clock_cpu(cpu) - irqtime->irq_start_time;
irqtime->irq_start_time += delta;
- u64_stats_update_begin(&irqtime->sync);
/*
* We do not account for softirq time from ksoftirqd here.
* We want to continue accounting softirq time to ksoftirqd thread
* in that case, so as not to confuse scheduler with a special task
* that do not consume any time, but still wants to run.
*/
- if (hardirq_count()) {
- cpustat[CPUTIME_IRQ] += delta;
- irqtime->tick_delta += delta;
- } else if (in_serving_softirq() && curr != this_cpu_ksoftirqd()) {
- cpustat[CPUTIME_SOFTIRQ] += delta;
- irqtime->tick_delta += delta;
- }
-
- u64_stats_update_end(&irqtime->sync);
+ if (hardirq_count())
+ irqtime_account_delta(irqtime, delta, CPUTIME_IRQ);
+ else if (in_serving_softirq() && curr != this_cpu_ksoftirqd())
+ irqtime_account_delta(irqtime, delta, CPUTIME_SOFTIRQ);
}
EXPORT_SYMBOL_GPL(irqtime_account_irq);