linux-kernel - [PATCH 0/3] sched: Fix irq accounting for CONFIG_IRQ_TIME

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Message-Id: <20240923090028.16368-1-laoar.shao@gmail.com>
Date: Mon, 23 Sep 2024 17:00:25 +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
Cc: linux-kernel@...r.kernel.org,
	Yafang Shao <laoar.shao@...il.com>
Subject: [PATCH 0/3] sched: Fix irq accounting for CONFIG_IRQ_TIME_ACCOUNTING

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.

Yafang Shao (3):
  sched: Fix cgroup irq accounting for CONFIG_IRQ_TIME_ACCOUNTING
  sched: Define sched_clock_irqtime as static key
  sched: Don't account irq time if sched_clock_irqtime is disabled

 kernel/sched/core.c    | 44 ++++++++++++++++++++++--------------------
 kernel/sched/cputime.c | 26 +++++++++++++------------
 kernel/sched/sched.h   |  1 +
 3 files changed, 38 insertions(+), 33 deletions(-)

-- 
2.43.5