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Date:   Tue, 24 Aug 2021 11:19:43 -0400
From:   Dave Jones <davej@codemonkey.org.uk>
To:     Peter Zijlstra <peterz@infradead.org>
Cc:     Linux Kernel <linux-kernel@vger.kernel.org>,
        Johannes Weiner <hannes@cmpxchg.org>,
        Linus Torvalds <torvalds@linux-foundation.org>
Subject: Re: 5.14-rc breaks iotop swap io monitoring.
Message-ID: <20210824151943.GA386@codemonkey.org.uk>
Mail-Followup-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>
References: <20210824031648.GA2725@codemonkey.org.uk>
 <YSSuVO47ieWDfWMQ@hirez.programming.kicks-ass.net>
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On Tue, Aug 24, 2021 at 10:31:16AM +0200, Peter Zijlstra wrote:
 > On Mon, Aug 23, 2021 at 11:16:48PM -0400, Dave Jones wrote:
 > > I just noticed that in 5.14-rc running iotop, it complains on startup
 > > that "CONFIG_TASK_DELAY_ACCT not enabled in kernel, cannot determine
 > > SWAPIN and IO %" and sure enough a bunch of columns show up as
 > > 'unavailable'.
 > > 
 > > My suspicion is this commit, which I've not confirmed yet as it doesn't
 > > cleanly revert.  I'll poke at it some more in the morning, but figured
 > > I'd bring it up sans-evidence in the hope that I'll wake up to someone
 > > having an Ah-ha moment.
 > 
 > 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.

	Dave