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Groups > linux.kernel > #1616279
| From | Luiz Capitulino <lcapitulino@redhat.com> |
|---|---|
| Newsgroups | linux.kernel |
| Subject | Re: [BUG nohz]: wrong user and system time accounting |
| Date | 2017-04-04 20:10 +0200 |
| Message-ID | <tsB3Y-8pK-7@gated-at.bofh.it> (permalink) |
| References | (7 earlier) <trb1T-QL-3@gated-at.bofh.it> <tre9r-2KJ-3@gated-at.bofh.it> <trhK1-5pA-1@gated-at.bofh.it> <tsc5B-cE-45@gated-at.bofh.it> <tsfwv-2wG-49@gated-at.bofh.it> |
| Organization | Red Hat |
On Mon, 3 Apr 2017 15:06:13 -0400 Luiz Capitulino <lcapitulino@redhat.com> wrote: > On Mon, 3 Apr 2017 17:23:17 +0200 > Frederic Weisbecker <fweisbec@gmail.com> wrote: > > > Do you observe aligned ticks with trace events (hrtimer_expire_entry)? > > > > You might want to enforce the global clock to trace that: > > > > echo "global" > /sys/kernel/debug/tracing/trace_clock > > I've used the same trace points & debugging code I've been using to debug > this issue, and this what I'm seeing: > > stress-25757 [002] 2742.717507: function: enter_from_user_mode <-- apic_timer_interrupt > stress-25757 [002] 2742.717508: function: __context_tracking_exit <-- enter_from_user_mode > stress-25757 [002] 2742.717508: bprint: vtime_delta: diff=0 (now=4297409970 vtime_snap=4297409970) > stress-25757 [002] 2742.717509: function: smp_apic_timer_interrupt <-- apic_timer_interrupt > stress-25757 [002] 2742.717509: function: irq_enter <-- smp_apic_timer_interrupt > stress-25757 [002] 2742.717510: hrtimer_expire_entry: hrtimer=0xffffc900039fbe58 function=hrtimer_wakeup now=2742674000776 > stress-25757 [002] 2742.717514: function: irq_exit <-- smp_apic_timer_interrupt > cyclictest-25760 [002] 2742.717518: function: vtime_account_system <-- vtime_common_task_switch > cyclictest-25760 [002] 2742.717518: bprint: vtime_delta: diff=1000000 (now=4297409971 vtime_snap=4297409970) > cyclictest-25760 [002] 2742.717519: function: __vtime_account_system <-- vtime_account_system > cyclictest-25760 [002] 2742.717519: bprint: get_vtime_delta: vtime_snap=4297409970 now=4297409971 > cyclictest-25760 [002] 2742.717520: function: account_system_time <-- __vtime_account_system > cyclictest-25760 [002] 2742.717520: bprint: account_system_time: cputime=961981 > cyclictest-25760 [002] 2742.717521: function: __context_tracking_enter <-- do_syscall_64 > cyclictest-25760 [002] 2742.717522: function: vtime_user_enter <-- __context_tracking_enter > cyclictest-25760 [002] 2742.717522: bprint: vtime_delta: diff=0 (now=4297409971 vtime_snap=4297409971) > > CPU2 shows 98% system time while the other CPUs (from CPU3 to CPU7) > show 98% user time (they're all running the same workload). On further debugging this, I realized that I had overlooked something: the timer interrupt in this trace is not the tick, but cyclictest's timer (remember that the test-case consists of pinning cyclictest and a task hogging the CPU to the same CPU). I'm running cyclictest with -i 200. If I increase this to -i 1000, then I seem unable to reproduce the issue (caution: even with -i 200 it doesn't always happen. But it does usually happen after I restart the test-case a few times. However, I've never been able to reproduce with -i 1000). Now, if it's really cyclictest that's causing the timer interrupts to get aligned, I guess this might not have a solution? (note: I haven't been able to reproduce this on bare-metal).
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Re: [BUG nohz]: wrong user and system time accounting Rik van Riel <riel@redhat.com> - 2017-03-27 19:40 +0200
Re: [BUG nohz]: wrong user and system time accounting Wanpeng Li <kernellwp@gmail.com> - 2017-03-28 09:30 +0200
Re: [BUG nohz]: wrong user and system time accounting Rik van Riel <riel@redhat.com> - 2017-03-28 23:10 +0200
Re: [BUG nohz]: wrong user and system time accounting Luiz Capitulino <lcapitulino@redhat.com> - 2017-03-28 23:30 +0200
Re: [BUG nohz]: wrong user and system time accounting Wanpeng Li <kernellwp@gmail.com> - 2017-03-29 12:00 +0200
Re: [BUG nohz]: wrong user and system time accounting Frederic Weisbecker <fweisbec@gmail.com> - 2017-03-29 15:00 +0200
Re: [BUG nohz]: wrong user and system time accounting Rik van Riel <riel@redhat.com> - 2017-03-28 23:30 +0200
Re: [BUG nohz]: wrong user and system time accounting Luiz Capitulino <lcapitulino@redhat.com> - 2017-03-28 23:40 +0200
Re: [BUG nohz]: wrong user and system time accounting Rik van Riel <riel@redhat.com> - 2017-03-29 22:20 +0200
Re: [BUG nohz]: wrong user and system time accounting Frederic Weisbecker <fweisbec@gmail.com> - 2017-03-30 01:00 +0200
Re: [BUG nohz]: wrong user and system time accounting Rik van Riel <riel@redhat.com> - 2017-03-30 15:00 +0200
Re: [BUG nohz]: wrong user and system time accounting Wanpeng Li <kernellwp@gmail.com> - 2017-03-30 04:00 +0200
Re: [BUG nohz]: wrong user and system time accounting Frederic Weisbecker <fweisbec@gmail.com> - 2017-03-30 14:50 +0200
Re: [BUG nohz]: wrong user and system time accounting Mike Galbraith <efault@gmx.de> - 2017-03-30 15:20 +0200
Re: [BUG nohz]: wrong user and system time accounting Mike Galbraith <efault@gmx.de> - 2017-03-30 06:30 +0200
Re: [BUG nohz]: wrong user and system time accounting Wanpeng Li <kernellwp@gmail.com> - 2017-03-30 08:50 +0200
Re: [BUG nohz]: wrong user and system time accounting Wanpeng Li <kernellwp@gmail.com> - 2017-03-30 14:00 +0200
Re: [BUG nohz]: wrong user and system time accounting Mike Galbraith <efault@gmx.de> - 2017-03-30 14:40 +0200
Re: [BUG nohz]: wrong user and system time accounting Frederic Weisbecker <fweisbec@gmail.com> - 2017-03-30 15:40 +0200
Re: [BUG nohz]: wrong user and system time accounting Wanpeng Li <kernellwp@gmail.com> - 2017-03-30 16:10 +0200
Re: [BUG nohz]: wrong user and system time accounting Frederic Weisbecker <fweisbec@gmail.com> - 2017-03-30 16:30 +0200
Re: [BUG nohz]: wrong user and system time accounting Luiz Capitulino <lcapitulino@redhat.com> - 2017-03-30 23:30 +0200
Re: [BUG nohz]: wrong user and system time accounting Luiz Capitulino <lcapitulino@redhat.com> - 2017-03-31 22:10 +0200
Re: [BUG nohz]: wrong user and system time accounting Frederic Weisbecker <fweisbec@gmail.com> - 2017-04-01 01:30 +0200
Re: [BUG nohz]: wrong user and system time accounting Luiz Capitulino <lcapitulino@redhat.com> - 2017-04-01 05:20 +0200
Re: [BUG nohz]: wrong user and system time accounting Frederic Weisbecker <fweisbec@gmail.com> - 2017-04-03 17:30 +0200
Re: [BUG nohz]: wrong user and system time accounting Luiz Capitulino <lcapitulino@redhat.com> - 2017-04-03 21:10 +0200
Re: [BUG nohz]: wrong user and system time accounting Luiz Capitulino <lcapitulino@redhat.com> - 2017-04-04 20:10 +0200
Re: [BUG nohz]: wrong user and system time accounting Rik van Riel <riel@redhat.com> - 2017-04-05 16:30 +0200
Re: [BUG nohz]: wrong user and system time accounting Frederic Weisbecker <fweisbec@gmail.com> - 2017-03-30 15:00 +0200
Re: [BUG nohz]: wrong user and system time accounting Rik van Riel <riel@redhat.com> - 2017-03-30 15:10 +0200
Re: [BUG nohz]: wrong user and system time accounting Mike Galbraith <efault@gmx.de> - 2017-03-30 15:40 +0200
Re: [BUG nohz]: wrong user and system time accounting Frederic Weisbecker <fweisbec@gmail.com> - 2017-04-03 16:50 +0200
Re: [BUG nohz]: wrong user and system time accounting Mike Galbraith <efault@gmx.de> - 2017-04-04 09:40 +0200
Re: [BUG nohz]: wrong user and system time accounting Frederic Weisbecker <fweisbec@gmail.com> - 2017-03-30 15:50 +0200
Re: [BUG nohz]: wrong user and system time accounting Wanpeng Li <kernellwp@gmail.com> - 2017-03-30 00:50 +0200
Re: [BUG nohz]: wrong user and system time accounting Luiz Capitulino <lcapitulino@redhat.com> - 2017-03-30 04:20 +0200
Re: [BUG nohz]: wrong user and system time accounting Wanpeng Li <kernellwp@gmail.com> - 2017-03-30 14:30 +0200
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