Date: Fri, 26 Jun 2020 18:11:36 +0200 (CEST) From: Ronald Klop <ronald-lists@klop.ws> To: Bob Bishop <rb@gid.co.uk> Cc: Donald Wilde <dwilde1@gmail.com>, Peter Jeremy <peter@rulingia.com>, freebsd-stable <freebsd-stable@freebsd.org> Subject: Re: swap space issues Message-ID: <1140215402.1.1593187896838@localhost> In-Reply-To: <BAC0BDDA-7AC5-4029-B7D2-4C10DDB22028@gid.co.uk> 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> <BAC0BDDA-7AC5-4029-B7D2-4C10DDB22028@gid.co.uk>
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=20 Van: Bob Bishop <rb@gid.co.uk> Datum: vrijdag, 26 juni 2020 17:18 Aan: Peter Jeremy <peter@rulingia.com> CC: Donald Wilde <dwilde1@gmail.com>, freebsd-stable <freebsd-stable@freebs= d.org> Onderwerp: Re: swap space issues >=20 >=20 >=20 > > 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 th= e > > partitions. > =20 > If you configure a ZFS mirror in bsdinstall you get a swap partition per = drive by default. If you are running on multiple disks (a mirror) it can provide extra speed.= The example above is on the same disk. On one disk multiple swap partition= s will only spread the data non-optimal for the heads of the disk. >=20 > > 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 recommend= ed 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 real= istic > > limit is about half that. By default the realistic limit is about 4=C3= =97RAM (on > > 64-bit architectures), but this can be adjusted via kern.maxswzone (whi= ch > > 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 contro= ls > > the number of passes before the pageout daemon gives up and starts kill= ing > > processes when it can't free up enough RAM. "out of swap space" messag= es > > 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 >=20 >=20 > -- > Bob Bishop t: +44 (0)118 940 1243 > rb@gid.co.uk m: +44 (0)783 626 4518 >=20 >=20 >=20 >=20 > =20 >=20 >=20 > =20
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