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From:   Linus Torvalds <torvalds@linux-foundation.org>
Date:   Tue, 24 Aug 2021 09:34:02 -0700
Message-ID: <CAHk-=wiRe=JBK85HG7xtXH1XbOWcO1KYW8csuWfLuFoHKTqF0w@mail.gmail.com>
Subject: Re: 5.14-rc breaks iotop swap io monitoring.
To:     Dave Jones <davej@codemonkey.org.uk>,
        Peter Zijlstra <peterz@infradead.org>,
        Linux Kernel <linux-kernel@vger.kernel.org>,
        Johannes Weiner <hannes@cmpxchg.org>,
        Linus Torvalds <torvalds@linux-foundation.org>
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On Tue, Aug 24, 2021 at 8:19 AM Dave Jones <davej@codemonkey.org.uk> wrote:
>
> On Tue, Aug 24, 2021 at 10:31:16AM +0200, Peter Zijlstra wrote:
>  >
>  > If you need DELAYACCT I'm thinking:
>  >
>  >   e4042ad49235 ("delayacct: Default disabled")
>  >
>  > and
>  >
>  >   0cd7c741f01d ("delayacct: Add sysctl to enable at runtime")
>
> That does sound more relevant. however, even after echo 1  > /proc/sys/kernel/task_delayacct,
> it still fails in the same way.

Hmm.

What happens if you boot with the 'delayacct' kernel parameter.

Even if you enable it at run-time, processes that have been started
before it was enabled won't actually have the 'tsk->delays'
allocation. So I'm not sure how effective the run-time thing is.

            Linus