linux-kernel - Re: [PATCH 7/6] delayacct: Add sysctl to enable at runtime

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Message-ID: <20210512114035.GH3672@suse.de>
Date:   Wed, 12 May 2021 12:40:35 +0100
From:   Mel Gorman <mgorman@...e.de>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     tglx@...utronix.de, mingo@...nel.org, juri.lelli@...hat.com,
        vincent.guittot@...aro.org, dietmar.eggemann@....com,
        rostedt@...dmis.org, bsegall@...gle.com, bristot@...hat.com,
        bsingharora@...il.com, pbonzini@...hat.com, maz@...nel.org,
        linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        riel@...riel.com, hannes@...xchg.org,
        Jonathan Corbet <corbet@....net>
Subject: Re: [PATCH 7/6] delayacct: Add sysctl to enable at runtime

On Mon, May 10, 2021 at 02:05:13PM +0200, Peter Zijlstra wrote:
> 
> Just like sched_schedstats, allow runtime enabling (and disabling) of
> delayacct. This is useful if one forgot to add the delayacct boot time
> option.
> 
> Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
> ---
>  Documentation/accounting/delay-accounting.rst |    6 ++--
>  kernel/delayacct.c                            |   36 ++++++++++++++++++++++++--
>  kernel/sysctl.c                               |   12 ++++++++
>  3 files changed, 50 insertions(+), 4 deletions(-)
> 

Update sysctl/kernel.rst?

diff --git a/Documentation/admin-guide/sysctl/kernel.rst b/Documentation/admin-guide/sysctl/kernel.rst
index 1d56a6b73a4e..5d9193bd8d27 100644
--- a/Documentation/admin-guide/sysctl/kernel.rst
+++ b/Documentation/admin-guide/sysctl/kernel.rst
@@ -1087,6 +1087,13 @@ Model available). If your platform happens to meet the
 requirements for EAS but you do not want to use it, change
 this value to 0.
 
+sched_delayacct
+===============
+
+Enables/disables task delay accounting (see
+:doc:`accounting/delay-accounting.rst`). Enabling this feature incurs
+a small amount of overhead in the scheduler but is useful for debugging
+and performance tuning. It is required by some tools such as iotop.
 
 sched_schedstats
 ================

-- 
Mel Gorman
SUSE Labs