Date: Tue, 8 Jun 2021 12:26:45 +0300 From: Andriy Gapon <avg@FreeBSD.org> To: Chris <bsd-lists@bsdforge.com>, Dewayne Geraghty <dewayne@heuristicsystems.com.au> Cc: Dave Hayes <dave@jetcafe.org>, freebsd-stable@freebsd.org Subject: Re: Where might memory be reported? Message-ID: <b82f1c63-d227-d85d-d8ed-3a5f89a9cfdf@FreeBSD.org> In-Reply-To: <7a70082c6e7e8f948e5c6f92c70174fc@bsdforge.com> References: <20210606160913.167e6c0a@bigus.dream-tech.com> <20210607115334.6e9d1178@bigus.dream-tech.com> <6c174c830019d133fbb4daefe442fb40@bsdforge.com> <bba08248-f898-cead-8df5-a52b1e14257a@heuristicsystems.com.au> <7a70082c6e7e8f948e5c6f92c70174fc@bsdforge.com>
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On 08/06/2021 10:39, Chris wrote: > On 2021-06-07 22:58, Dewayne Geraghty wrote: >> This issue was raised in April '21 by Andriy Gapon title "stable/13, vm >> page counts do not add up". >> >> This was mentioned >> https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=253281 >> though its probably more of an affirmation of a symptom. (reminder to >> adjust status) >> >> More relevant is >> https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=234559 >> where Mark Johnson advised (in Feb '19) >> "I've thought about this some more and decided to close this bug WONTFIX >> for now. Basically, we started lazily dequeuing wired pages to avoid >> the page queue synchronization cost incurred by frequent wirings. The >> result is that wired pages may temporarily be counted as >> active/inactive/laundry despite not being reclaimable. Maintaining the >> previous behaviour wrt statistics would introduce synchronization >> overhead that we've been trying to avoid in past and future work. I >> don't plan to change the current behaviour and there doesn't seem to be >> a compelling reason to do so, at least based on this report. If you or >> anyone else would like to discuss this further or describe a use-case >> that depends on the old behaviour, please feel free to re-open the bug." > tl;dr > I recognize this needs work. But it's a GREAT DEAL of work, and I currently > have much shinier things on my to-do list. ;-) > > No offense to Mark. He's doing a tremendous job. I just couldn't resist. :-) Just to clarify, Mark was commenting on small discrepancies (deviations, fluctuations) that can happen because of lazy statistics. The large and persistent (and growing) mismatch seems like a different problem. -- Andriy Gapon
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