unix: Use a dedicated mtx pool for vnode name locks
ClosedPublic
Actions

Authored by jhb on Sep 26 2024, 1:22 AM.

Details

Reviewers

Commits

rGc08e016f000c: unix: Use a dedicated mtx pool for vnode name locks

Summary

mtxpool_sleep should be used as a leaf lock since it is a general
purpose pool shared across many consumers. Holding a pool lock while
acquiring other locks (e.g. the socket buffer lock in soreserve()) can
trigger LOR warnings for unrelated code.

Diff Detail

Repository

rG FreeBSD src repository

Lint

Lint Skipped

Unit

Tests Skipped

Build Status

Buildable 59604
Build 56491: arc lint + arc unit

Event Timeline

jhb created this revision.Sep 26 2024, 1:22 AM

Herald added subscribers: olce, imp. · View Herald TranscriptSep 26 2024, 1:22 AM

jhb requested review of this revision.Sep 26 2024, 1:22 AM

Harbormaster completed remote builds in B59604: Diff 143735.Sep 26 2024, 1:22 AM

The LORs I was seeing before were mitigated by rGaec2ae8b57fc638fa3ba9fac9d2067f2049ab613. However, I do think in general that locks from the global mutex pools should only be used as leaf locks.

Also, the count of 1024 locks might be too high here. I just copied the default size of the mtxpool_sleep pool. We could use a smaller value like 128 or 64 if we don't think these will be contested very often.

We definitely should go with a much lower value. The pool is used only during connect/close/detach of a named socket, which is definitely not a hot path in any sane workload.

This revision is now accepted and ready to land.Sep 30 2024, 7:04 PM

Ok, I'll drop it to 32 for commit then.

Closed by commit rGc08e016f000c: unix: Use a dedicated mtx pool for vnode name locks (authored by jhb). · Explain WhyOct 2 2024, 7:14 PM

This revision was automatically updated to reflect the committed changes.

jhb added a commit: rGc08e016f000c: unix: Use a dedicated mtx pool for vnode name locks.