Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
IronPort-SDR: QE8h0f/MjikkdTDlK+FY15167lYE5vqkpTeJMBNxUEQaW5mYfCRwRELPYLz7C259TPR+7jAo1M
 ZOOBysg4gcicXutcQHE+ZV/qNrb9CDPzXtVZh/e57fSTVt+J/xSRmJ6HpQu0Dlhjmt3p7+LWHF
 Hl4bYW2a2P8GT/2l10de/HLdLuoNNuZfvRNAy/CsIBasU5jJUNBdKy7zNjQNwpUONoLgIhxcbM
 vkbcI7swL4j+YgvVfXdqNepjpv+NYvysXybZB19eby3IauOfPwhg4ykmOLaigi10v2A6svnVSr
 Jjc04ejs/6Tp/wEpqseSMrYx
From:   Hasegawa Hitomi <hasegawa-hitomi@fujitsu.com>
To:     frederic@kernel.org
Cc:     bristot@redhat.com, bsegall@google.com, dietmar.eggemann@arm.com,
        fweisbec@gmail.com, juri.lelli@redhat.com,
        linux-kernel@vger.kernel.org, mgorman@suse.de, mingo@kernel.org,
        peterz@infradead.org, rostedt@goodmis.org, tglx@linutronix.de,
        vincent.guittot@linaro.org,
        Hasegawa Hitomi <hasegawa-hitomi@fujitsu.com>
Subject: [RFC][PATCH 0/1] sched/cputime: Improve getrusage(RUSAGE_THREAD) with nohz_full
Date:   Tue, 28 Sep 2021 14:08:03 +0900
Message-Id: <20210928050804.4156102-1-hasegawa-hitomi@fujitsu.com>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Precedence: bulk

Frederic, seems busy, so I create the proper patch, would you please add
your Signed-off-by: if this fix is okey.
This patch is a fix proposed in the following thread [1].


The getrusage(RUSAGE_THREAD) with nohz_full returns shorter utime/stime
than the actual time.

In the current implementation, task_cputime_adjusted() calls task_cputime()
to get the "current" utime and stime, then calls cputime_adjust () to adjust
the sum of utime and stime to be equal to cputime.sum_exec_runtime.
In nohz_full, sum_exec_runtime is not updated regularly, which is the cause
of this discrepancy.

This patch add a process to update sum_exec_runtime after getting
the information from "current" and before adjusting. 
This addition applies only when run with nohz_full.

Thanks.
Hitomi Hasegawa

[1] https://lore.kernel.org/lkml/OSBPR01MB21837C8931D90AE55AF4A955EB529@OSBPR01MB2183.jpnprd01.prod.outlook.com/

--

Hasegawa Hitomi (1):
  sched/cputime: Improve getrusage(RUSAGE_THREAD) with nohz_full

 include/linux/sched/cputime.h |  5 +++--
 kernel/sched/cputime.c        | 12 +++++++++---
 2 files changed, 12 insertions(+), 5 deletions(-)

-- 
2.25.1