Date: Sun, 3 Oct 2021 22:07:22 -0600 From: Alan Somers <asomers@freebsd.org> To: Mateusz Guzik <mjguzik@gmail.com> Cc: Michael Jung <mikej@mikej.com>, John Baldwin <jhb@freebsd.org>, FreeBSD Current <freebsd-current@freebsd.org>, owner-freebsd-current@freebsd.org Subject: Re: witness_lock_list_get: witness exhausted Message-ID: <CAOtMX2i4Rpc2czW3gwRLh987OoXz2wnjQEpdrALUsXJez38srA@mail.gmail.com> In-Reply-To: <CAGudoHF0gG40SMOvQve1XpX%2Br_5oQWt8L43p_GXNmHmVEHo7-g@mail.gmail.com> References: <6eecc842ba7a37af6b2ffe146dfd91da@mikej.com> <1684681.MCyL5Ev91y@ralph.baldwin.cx> <54018b1b2feaab3b05d7ed406eb8273c@mikej.com> <CAGudoHF0gG40SMOvQve1XpX%2Br_5oQWt8L43p_GXNmHmVEHo7-g@mail.gmail.com>
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On Mon, Jan 8, 2018 at 5:31 PM Mateusz Guzik <mjguzik@gmail.com> wrote: > > On Tue, Jan 9, 2018 at 12:41 AM, Michael Jung <mikej@mikej.com> wrote: > > > On 2018-01-08 13:39, John Baldwin wrote: > > > >> On Tuesday, November 28, 2017 02:46:03 PM Michael Jung wrote: > >> > >>> Hi! > >>> > >>> I've recently up'd my processor count on our poudriere box and have > >>> started noticing the error > >>> "witness_lock_list_get: witness exhausted" on the console. The kernel > >>> *DOES NOT* crash but I > >>> thought the report may be useful to someone. > >>> > >>> $ uname -a > >>> FreeBSD poudriere 12.0-CURRENT FreeBSD 12.0-CURRENT #1 r325999: Sun Nov > >>> 19 18:41:20 EST 2017 > >>> mikej@poudriere:/usr/obj/usr/src/amd64.amd64/sys/GENERIC amd64 > >>> > >>> The machine is pretty busy running four poudriere build instances. > >>> > >>> last pid: 76584; load averages: 115.07, 115.96, 98.30 > >>> > >>> up 6+07:32:59 14:44:03 > >>> 763 processes: 117 running, 581 sleeping, 2 zombie, 63 lock > >>> CPU: 59.0% user, 0.0% nice, 40.7% system, 0.1% interrupt, 0.1% idle > >>> Mem: 12G Active, 2003M Inact, 44G Wired, 29G Free > >>> ARC: 28G Total, 11G MFU, 16G MRU, 122M Anon, 359M Header, 1184M Other > >>> 25G Compressed, 32G Uncompressed, 1.24:1 Ratio > >>> > >>> Let me know what additional information I might supply. > >>> > >> > >> This just means that WITNESS stopped working because it ran out of > >> pre-allocated objects. In particular the objects used to track how > >> many locks are held by how many threads: > >> > >> /* > >> * XXX: This is somewhat bogus, as we assume here that at most 2048 > >> threads > >> * will hold LOCK_NCHILDREN locks. We handle failure ok, and we should > >> * probably be safe for the most part, but it's still a SWAG. > >> */ > >> #define LOCK_NCHILDREN 5 > >> #define LOCK_CHILDCOUNT 2048 > >> > >> Probably the '2048' (max number of concurrent threads) needs to scale with > >> MAXCPU. 2048 threads is probably a bit low on big x86 boxes. > >> > > > > > > Thank you for you explanation. We are expanding our ESXi cluster and even > > though with standard edition I can only assign 64 vCPU's to a guest and as > > much > > RAM as I want, I do like to help with edge cases if I can make them occur > > pushing > > boundaries as I can towards additianional improvements in FreeBSD. > > > > Can you apply this and re-run the test? > > https://people.freebsd.org/~mjg/witness.diff > > It bumps the counters to be "high enough" but also starts tracking usage. > If you get > the message again, bump the values even higher. > > Once you get a complete poudriere run which did not result in the problem, > do: > $ sysctl debug.witness.list_used debug.witness.list_max_used > > to dump the actual usage. This is a nice little patch. Can we commit to head? Even better would be if LOCK_CHILDCOUNT could be a tunable. On my largish system, here's what I get shortly after boot: debug.witness.list_max_used: 8432 debug.witness.list_used: 8420 -Alan
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