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Date:   Tue, 24 Aug 2021 17:33:42 -0400
From:   Dave Jones <davej@codemonkey.org.uk>
To:     Linus Torvalds <torvalds@linux-foundation.org>
Cc:     Peter Zijlstra <peterz@infradead.org>,
        Linux Kernel <linux-kernel@vger.kernel.org>,
        Johannes Weiner <hannes@cmpxchg.org>
Subject: Re: 5.14-rc breaks iotop swap io monitoring.
Message-ID: <20210824213342.GA1708@codemonkey.org.uk>
Mail-Followup-To: Dave Jones <davej@codemonkey.org.uk>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Peter Zijlstra <peterz@infradead.org>,
        Linux Kernel <linux-kernel@vger.kernel.org>,
        Johannes Weiner <hannes@cmpxchg.org>
References: <20210824031648.GA2725@codemonkey.org.uk>
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 <20210824151943.GA386@codemonkey.org.uk>
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On Tue, Aug 24, 2021 at 09:34:02AM -0700, Linus Torvalds wrote:
 > 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.

Yeah that boot option does make iotop work again.

	Dave