Re: witness_lock_list_get: witness exhausted
- In reply to: Alan Somers : "Re: witness_lock_list_get: witness exhausted"
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Date: Mon, 04 Oct 2021 11:27:51 UTC
Just take it and change as you see fit, I don't have time to work on it. On 10/4/21, Alan Somers <asomers@freebsd.org> wrote: > 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 > -- Mateusz Guzik <mjguzik gmail.com>