From: Peter Zijlstra <peterz@infradead.org>
To: Frederic Weisbecker <frederic@kernel.org>
Cc: LKML <linux-kernel@vger.kernel.org>,
Wanpeng Li <wanpengli@tencent.com>,
Thomas Gleixner <tglx@linutronix.de>,
Yauheni Kaliuta <yauheni.kaliuta@redhat.com>,
Ingo Molnar <mingo@kernel.org>, Rik van Riel <riel@redhat.com>
Subject: Re: [PATCH 08/25] vtime: Exit vtime before exit_notify()
Date: Tue, 20 Nov 2018 14:54:59 +0100 [thread overview]
Message-ID: <20181120135459.GR2131@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <1542163569-20047-9-git-send-email-frederic@kernel.org>
On Wed, Nov 14, 2018 at 03:45:52AM +0100, Frederic Weisbecker wrote:
> diff --git a/include/linux/sched.h b/include/linux/sched.h
> index d458d65..27e0544 100644
> --- a/include/linux/sched.h
> +++ b/include/linux/sched.h
> @@ -265,6 +265,8 @@ struct task_cputime {
> enum vtime_state {
> /* Task is sleeping or running in a CPU with VTIME inactive: */
> VTIME_INACTIVE = 0,
> + /* Task has passed exit_notify() */
> + VTIME_DEAD,
How does it make sense for VTIME_DEAD > VTIME_INACTIVE ?
> /* Task is idle */
> VTIME_IDLE,
> /* Task runs in kernelspace in a CPU with VTIME active: */
> diff --git a/kernel/sched/cputime.c b/kernel/sched/cputime.c
> index f64afd7..a0c3a82 100644
> --- a/kernel/sched/cputime.c
> +++ b/kernel/sched/cputime.c
> @@ -813,17 +813,31 @@ void vtime_task_switch_generic(struct task_struct *prev)
> {
> struct vtime *vtime = &prev->vtime;
>
> - write_seqcount_begin(&vtime->seqcount);
> - if (vtime->state == VTIME_IDLE)
> - vtime_account_idle(prev);
> - else
> - __vtime_account_kernel(prev, vtime);
> - vtime->state = VTIME_INACTIVE;
> - vtime->cpu = -1;
> - write_seqcount_end(&vtime->seqcount);
> + /*
> + * Flush the prev task vtime, unless it has passed
> + * vtime_exit_task(), in which case there is nothing
> + * left to account.
> + */
> + if (vtime->state != VTIME_DEAD) {
> + write_seqcount_begin(&vtime->seqcount);
> + if (vtime->state == VTIME_IDLE)
> + vtime_account_idle(prev);
> + else
> + __vtime_account_kernel(prev, vtime);
> + vtime->state = VTIME_INACTIVE;
> + vtime->cpu = -1;
> + write_seqcount_end(&vtime->seqcount);
> + }
>
> vtime = ¤t->vtime;
>
> + /*
> + * Ignore the next task if it has been preempted after
> + * vtime_exit_task().
> + */
> + if (vtime->state == VTIME_DEAD)
> + return;
> +
> write_seqcount_begin(&vtime->seqcount);
> if (is_idle_task(current))
> vtime->state = VTIME_IDLE;
Bit inconsistent; having the one as a indent and the other as an early
return.
> @@ -850,6 +864,30 @@ void vtime_init_idle(struct task_struct *t, int cpu)
> local_irq_restore(flags);
> }
>
> +/*
> + * This is the final settlement point after which we don't account
> + * anymore vtime for this task.
> + */
> +void vtime_exit_task(struct task_struct *t)
> +{
> + struct vtime *vtime = &t->vtime;
> + unsigned long flags;
Note that the code in vtime_task_switch_generic() (above) relies on @t
== current (which is true, but not explicit).
> + local_irq_save(flags);
> + write_seqcount_begin(&vtime->seqcount);
> + /*
> + * A task that has never run on a nohz_full CPU hasn't
> + * been tracked by vtime. Thus it's in VTIME_INACTIVE
> + * state. Nothing to account for it.
> + */
> + if (vtime->state != VTIME_INACTIVE)
> + vtime_account_system(t, vtime);
> + vtime->state = VTIME_DEAD;
> + vtime->cpu = -1;
> + write_seqcount_end(&vtime->seqcount);
> + local_irq_restore(flags);
> +}
> +
> u64 task_gtime(struct task_struct *t)
> {
> struct vtime *vtime = &t->vtime;
> --
> 2.7.4
>
next prev parent reply other threads:[~2018-11-20 13:55 UTC|newest]
Thread overview: 45+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-11-14 2:45 [PATCH 00/25] sched/nohz: Make kcpustat vtime aware (Fix kcpustat on nohz_full) Frederic Weisbecker
2018-11-14 2:45 ` [PATCH 01/25] sched/vtime: Fix guest/system mis-accounting on task switch Frederic Weisbecker
2018-11-14 2:45 ` [PATCH 02/25] sched/vtime: Protect idle accounting under vtime seqcount Frederic Weisbecker
2018-11-20 13:19 ` Peter Zijlstra
2018-11-14 2:45 ` [PATCH 03/25] vtime: Rename vtime_account_system() to vtime_account_kernel() Frederic Weisbecker
2018-11-14 2:45 ` [PATCH 04/25] vtime: Spare a seqcount lock/unlock cycle on context switch Frederic Weisbecker
2018-11-20 13:25 ` Peter Zijlstra
2019-09-25 14:42 ` Frederic Weisbecker
2018-11-14 2:45 ` [PATCH 05/25] sched/vtime: Record CPU under seqcount for kcpustat needs Frederic Weisbecker
2018-11-14 2:45 ` [PATCH 06/25] sched/cputime: Add vtime idle task state Frederic Weisbecker
2018-11-14 2:45 ` [PATCH 07/25] sched/cputime: Add vtime guest " Frederic Weisbecker
2018-11-14 2:45 ` [PATCH 08/25] vtime: Exit vtime before exit_notify() Frederic Weisbecker
2018-11-20 13:54 ` Peter Zijlstra [this message]
2018-11-14 2:45 ` [PATCH 09/25] kcpustat: Track running task following vtime sequences Frederic Weisbecker
2018-11-20 13:58 ` Peter Zijlstra
2018-11-14 2:45 ` [PATCH 10/25] context_tracking: Remove context_tracking_active() Frederic Weisbecker
2018-11-14 2:45 ` [PATCH 11/25] context_tracking: s/context_tracking_is_enabled/context_tracking_enabled() Frederic Weisbecker
2018-11-14 2:45 ` [PATCH 12/25] context_tracking: Rename context_tracking_is_cpu_enabled() to context_tracking_enabled_this_cpu() Frederic Weisbecker
2018-11-14 2:45 ` [PATCH 13/25] context_tracking: Introduce context_tracking_enabled_cpu() Frederic Weisbecker
2018-11-20 14:02 ` Peter Zijlstra
2018-11-14 2:45 ` [PATCH 14/25] sched/vtime: Rename vtime_accounting_cpu_enabled() to vtime_accounting_enabled_this_cpu() Frederic Weisbecker
2018-11-14 2:45 ` [PATCH 15/25] sched/vtime: Introduce vtime_accounting_enabled_cpu() Frederic Weisbecker
2018-11-20 14:04 ` Peter Zijlstra
2018-11-14 2:46 ` [PATCH 16/25] sched/cputime: Allow to pass cputime index on user/guest accounting Frederic Weisbecker
2018-11-14 2:46 ` [PATCH 17/25] sched/cputime: Standardize the kcpustat index based accounting functions Frederic Weisbecker
2018-11-14 2:46 ` [PATCH 18/25] vtime: Track nice-ness on top of context switch Frederic Weisbecker
2018-11-20 14:09 ` Peter Zijlstra
2018-11-14 2:46 ` [PATCH 19/25] sched/vite: Handle nice updates under vtime Frederic Weisbecker
2018-11-20 14:17 ` Peter Zijlstra
2018-11-26 15:53 ` Frederic Weisbecker
2018-11-26 16:11 ` Peter Zijlstra
2018-11-26 18:41 ` Frederic Weisbecker
2018-11-14 2:46 ` [PATCH 20/25] sched/kcpustat: Introduce vtime-aware kcpustat accessor Frederic Weisbecker
2018-11-20 14:23 ` Peter Zijlstra
2018-11-20 22:40 ` Frederic Weisbecker
2018-11-21 8:18 ` Peter Zijlstra
2018-11-21 8:35 ` Peter Zijlstra
2018-11-21 16:33 ` Frederic Weisbecker
2018-11-14 2:46 ` [PATCH 21/25] procfs: Use vtime aware " Frederic Weisbecker
2018-11-20 14:24 ` Peter Zijlstra
2018-11-20 22:31 ` Frederic Weisbecker
2018-11-14 2:46 ` [PATCH 22/25] cpufreq: " Frederic Weisbecker
2018-11-14 2:46 ` [PATCH 23/25] leds: Use vtime aware kcpustat accessors Frederic Weisbecker
2018-11-14 2:46 ` [PATCH 24/25] rackmeter: " Frederic Weisbecker
2018-11-14 2:46 ` [PATCH 25/25] sched/vtime: Clarify vtime_task_switch() argument layout Frederic Weisbecker
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