Date: Thu, 9 Aug 2018 13:09:00 -0400 From: Mark Johnston <markj@freebsd.org> To: Mark Millard <marklmi@yahoo.com> Cc: bob prohaska <fbsd@www.zefox.net>, freebsd-arm@freebsd.org Subject: Re: RPI3 swap experiments ["was killed: out of swap space" with: "v_free_count: 5439, v_inactive_count: 1"] Message-ID: <20180809170900.GD68459@raichu> In-Reply-To: <915DFC7F-7AC9-484F-8619-C386FF077769@yahoo.com> References: <6BFE7B77-A0E2-4FAF-9C68-81951D2F6627@yahoo.com> <20180802002841.GB99523@www.zefox.net> <20180802015135.GC99523@www.zefox.net> <EC74A5A6-0DF4-48EB-88DA-543FD70FEA07@yahoo.com> <20180806155837.GA6277@raichu> <20180808153800.GF26133@www.zefox.net> <20180808204841.GA19379@raichu> <20180809065648.GB30347@www.zefox.net> <20180809152152.GC68459@raichu> <915DFC7F-7AC9-484F-8619-C386FF077769@yahoo.com>
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On Thu, Aug 09, 2018 at 09:21:38AM -0700, Mark Millard wrote: > Would something like the patch that produced the messages > like: > > waited 3s for async swap write > waited 3s for swap buffer > > be appropriate as able to be enabled via a sysctl or in > some other way? In other words: in the source code by standard, > off by default, but able to be enabled without patching, > possibly without rebuilding? Yes, I think so. We don't have a lot of visibility into the behaviour of the pageout threads, and I have some ideas on how to improve that. Swap I/O latency measurements are something I've wanted in the past. > I ask because I've been thinking of having such on the > FreeBSD's where I buildworld buildkernel and use poudriere-devel > for port builds. It might warning me of marginal contexts and > help explain any OOM kills that might occur. (Somethings > things are difficult or time consuming to reproduce.) > > If monitored at the time, it might even help identify contexts > that "machine-gun down requests" in environments were such can > be a problem for swapping.
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