Date: Fri, 26 Jun 2020 16:18:05 +0100 From: Bob Bishop <rb@gid.co.uk> To: Peter Jeremy <peter@rulingia.com> Cc: Donald Wilde <dwilde1@gmail.com>, freebsd-stable <freebsd-stable@freebsd.org> Subject: Re: swap space issues Message-ID: <BAC0BDDA-7AC5-4029-B7D2-4C10DDB22028@gid.co.uk> In-Reply-To: <20200626102331.GA6406@server.rulingia.com> References: <CAEC7391qs%2BA-jMpR1RyvR-BmnLyiksXHkQUjsGeePuEZJfMciw@mail.gmail.com> <20200625000410.GA10210@eureka.lemis.com> <CAEC7390VDxbYSY%2B4_fEaYxwdSPzbFWUVTdHw=vbAgq%2Bnmv09Vw@mail.gmail.com> <20200625025248.GB10210@eureka.lemis.com> <CAEC73938Wjb5MHvLW36PdoAy_nso-tSN51AhUYydC6qxY99pog@mail.gmail.com> <E8763B97-2DB7-4C77-864D-08155168E352@gromit.dlib.vt.edu> <CAEC7391AHKXd0KfJdUGKMv1QRh_AtA1BrtqaQwy3dXEoJEMoDw@mail.gmail.com> <20200626102331.GA6406@server.rulingia.com>
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[-- Attachment #1 --] > On 26 Jun 2020, at 11:23, Peter Jeremy <peter@rulingia.com> wrote: > > On 2020-Jun-25 11:30:31 -0700, Donald Wilde <dwilde1@gmail.com> wrote: >> Here's 'pstat -s' on the i3 (which registers as cpu HAMMER): >> >> Device 1K-blocks Used Avail Capacity >> /dev/ada0s1b 33554432 0 33554432 0% >> /dev/ada0s1d 33554432 0 33554432 0% >> Total 67108864 0 67108864 0% > > I strongly suggest you don't have more than one swap device on spinning > rust - the VM system will stripe I/O across the available devices and > that will give particularly poor results when it has to seek between the > partitions. If you configure a ZFS mirror in bsdinstall you get a swap partition per drive by default. > Also, you can't actually use 64GB swap with 4GB RAM. If you look back > through your boot messages, I expect you'll find messages like: > warning: total configured swap (524288 pages) exceeds maximum recommended amount (498848 pages). > warning: increase kern.maxswzone or reduce amount of swap. > or maybe: > WARNING: reducing swap size to maximum of xxxxMB per unit > > The absolute limit on swap space is vm.swap_maxpages pages but the realistic > limit is about half that. By default the realistic limit is about 4×RAM (on > 64-bit architectures), but this can be adjusted via kern.maxswzone (which > defines the #bytes of RAM to allocate to swzone structures - the actual > space allocated is vm.swzone). > > As a further piece of arcana, vm.pageout_oom_seq is a count that controls > the number of passes before the pageout daemon gives up and starts killing > processes when it can't free up enough RAM. "out of swap space" messages > generally mean that this number is too low, rather than there being a > shortage of swap - particularly if your swap device is rather slow. > > -- > Peter Jeremy -- Bob Bishop t: +44 (0)118 940 1243 rb@gid.co.uk m: +44 (0)783 626 4518 [-- Attachment #2 --] -----BEGIN PGP SIGNATURE----- iF0EARECAB0WIQR+a6Wh87I/iYwcbE+8xpPppLfFvwUCXvYRrQAKCRC8xpPppLfF v/+wAJ98LGxalqGfcgebkSivRY0gwlaSqQCg1NlPCKTAvIcxA93kEGCwOBOF0uI= =Htua -----END PGP SIGNATURE-----help
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