Date: Sat, 3 Mar 2018 08:26:05 -0800 From: bob prohaska <fbsd@www.zefox.net> To: Warner Losh <imp@bsdimp.com> Cc: Mike <the.lists@mgm51.com>, "freebsd-arm@freebsd.org" <freebsd-arm@freebsd.org>, bob prohaska <fbsd@www.zefox.net> Subject: Re: Is maximum swap usage tunable? Message-ID: <20180303162605.GA41874@www.zefox.net> In-Reply-To: <CANCZdfq_MpxjUyVd-=%2BMiAQAER4TeDh9irhx_evdXwa3yt3h0g@mail.gmail.com> References: <20180228170311.GA26187@www.zefox.net> <a759ecea-83f4-b0b2-7113-c39633f68637@mgm51.com> <20180228185517.GB26187@www.zefox.net> <8f422161-885e-aa91-eacd-018540222d65@mgm51.com> <20180228214301.GA29481@www.zefox.net> <b82801b8-bc29-414c-1170-621bb4a5d937@mgm51.com> <CANCZdfq_MpxjUyVd-=%2BMiAQAER4TeDh9irhx_evdXwa3yt3h0g@mail.gmail.com>
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On Fri, Mar 02, 2018 at 10:04:56AM -0700, Warner Losh wrote: > On Fri, Mar 2, 2018 at 9:19 AM, Mike <the.lists@mgm51.com> wrote: > > > > > buildworld is still running. I started it around 3PM (EST) on March 1. > > > > I'm seeing a lot of swap messages on the console. The text is: > > > > swap_pager: indefinite wait buffer: bufobj: 0, > > blkno: [varies], size: [varies] > > > This message comes from the swap pager when the I/O doesn't complete > quickly enough. It has nothing to do with sizes of the swap space. > > I've seen three causes for this: (1) The driver going crazy and not > completing I/Os it gets notified as being done; (2) The driver not having a > backstop timer on I/Os to fail them with timeout; (3) timeouts not firing > for the driver to fail the I/O up the stack. (4) when a drive suddenly slow > way way down (~100x or more slower), the I/O queues balloons and you can > get these. > Is there some sort of experiment which can distinguish hardware delays from software delays? For example, would logging gstat output shed any light? Thanks for reading, bob prohaska
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