vm_pageout: Add a chicken switch for multithreaded PQ_INACTIVE scanning
ClosedPublic
Actions

Authored by markj on Jan 7 2025, 7:25 PM.

Details

Reviewers

alc
kib
dougm

Commits

rG67e54a07e948: vm_pageout: Add a chicken switch for multithreaded PQ_INACTIVE scanning
rG55b343f4f9bc: vm_pageout: Add a chicken switch for multithreaded PQ_INACTIVE scanning

Summary

Right now we have the vm.pageout_cpus_per_thread tunable which controls
the number of threads to start up per CPU per NUMA domain, but after
booting, it's not possible to disable multi-threaded scanning.

There is at least one workload where this mechanism doesn't work well;
let's make it possible to disable it without a reboot, to simplify
troubleshooting.

Diff Detail

Repository

rG FreeBSD src repository

Lint

Lint Not Applicable

Unit

Tests Not Applicable

Event Timeline

markj created this revision.Jan 7 2025, 7:25 PM

Herald added a subscriber: imp. · View Herald TranscriptJan 7 2025, 7:25 PM

markj requested review of this revision.Jan 7 2025, 7:25 PM

Harbormaster completed remote builds in B61565: Diff 148910.Jan 7 2025, 7:25 PM

markj added a parent revision: D48376: vm_pageout: Make vmd_oom a bool.Jan 7 2025, 7:25 PM

kib added inline comments.Jan 7 2025, 7:41 PM

sys/vm/vm_pageout.c
2274	How a tunable would work there?

markj marked an inline comment as done.Jan 7 2025, 7:51 PM

markj added inline comments.

sys/vm/vm_pageout.c
2274	SYSCTL_ADD_BOOL fetches the value from the kenv, and it is applied if set. Empirically, it works, so long as the sysctl is added after the field is initialized of course.