linux-kernel - Re: [PATCH v3 bpf-next 0/4] sched: Fix irq accounting for CONFIG_IRQ_TIME

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Message-ID: <CALOAHbCoAMofLm6NV_7mT6XPZbck8Y11BveWrLV-t242Z4pbOw@mail.gmail.com>
Date: Wed, 23 Oct 2024 19:41:30 +0800
From: Yafang Shao <laoar.shao@...il.com>
To: mingo@...hat.com, peterz@...radead.org, juri.lelli@...hat.com, 
	vincent.guittot@...aro.org, dietmar.eggemann@....com, rostedt@...dmis.org, 
	bsegall@...gle.com, mgorman@...e.de, vschneid@...hat.com, hannes@...xchg.org, 
	surenb@...gle.com
Cc: cgroups@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 bpf-next 0/4] sched: Fix irq accounting for CONFIG_IRQ_TIME_ACCOUNTING

On Mon, Oct 14, 2024 at 11:11 AM Yafang Shao <laoar.shao@...il.com> wrote:
>
> After enabling CONFIG_IRQ_TIME_ACCOUNTING to track IRQ pressure in our
> container environment, we encountered several user-visible behavioral
> changes:
>
> - Interrupted IRQ/softirq time is not accounted for in the cpuacct cgroup
>
>   This breaks userspace applications that rely on CPU usage data from
>   cgroups to monitor CPU pressure. This patchset resolves the issue by
>   ensuring that IRQ/softirq time is accounted for in the cgroup of the
>   interrupted tasks.
>
> - getrusage(2) does not include time interrupted by IRQ/softirq
>
>   Some services use getrusage(2) to check if workloads are experiencing CPU
>   pressure. Since IRQ/softirq time is no longer charged to task runtime,
>   getrusage(2) can no longer reflect the CPU pressure caused by heavy
>   interrupts.
>
> This patchset addresses the first issue, which is relatively
> straightforward. However, the second issue remains unresolved, as there
> might be debate over whether interrupted time should be considered part of
> a task’s usage. Nonetheless, it is important to report interrupted time to
> the user via some metric, though that is a separate discussion.
>
> Changes:
> v2->v3:
> - Add a helper account_irqtime() to avoid redundant code (Johannes)
>
> v1->v2: https://lore.kernel.org/cgroups/20241008061951.3980-1-laoar.shao@gmail.com/
> - Fix lockdep issues reported by kernel test robot <oliver.sang@...el.com>
>
> v1: https://lore.kernel.org/all/20240923090028.16368-1-laoar.shao@gmail.com/
>
> Yafang Shao (4):
>   sched: Define sched_clock_irqtime as static key
>   sched: Don't account irq time if sched_clock_irqtime is disabled
>   sched, psi: Don't account irq time if sched_clock_irqtime is disabled
>   sched: Fix cgroup irq accounting for CONFIG_IRQ_TIME_ACCOUNTING
>
>  kernel/sched/core.c    | 78 +++++++++++++++++++++++++++++-------------
>  kernel/sched/cputime.c | 16 ++++-----
>  kernel/sched/psi.c     | 12 ++-----
>  kernel/sched/sched.h   |  1 +
>  kernel/sched/stats.h   |  7 ++--
>  5 files changed, 69 insertions(+), 45 deletions(-)
>
> --
> 2.43.5
>

Hello Peter, Hello Ingo,

Do you have comments or any suggestions on this fix?

-- 
Regards
Yafang