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Differential D46943

vm_page: Use atomic loads for cmpset loops
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Authored by markj on Fri, Oct 4, 3:07 PM.

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Reviewers
alc
kib
dougm
Summary

Make sure that the compiler loads the initial value value only once.
Because atomic_fcmpset is used to load the value for subsequent
iterations, this is probably not needed, but we should not rely on that.

I verified that code generated for an amd64 GENERIC kernel does not
change.

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Repository
rG FreeBSD src repository
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Build Status
Buildable 59757
Build 56643: arc lint + arc unit

Event Timeline

markj created this revision.Fri, Oct 4, 3:07 PM
Herald added a subscriber: imp. · View Herald TranscriptFri, Oct 4, 3:07 PM
Harbormaster completed remote builds in B59757: Diff 144250.Fri, Oct 4, 3:07 PM
markj requested review of this revision.Fri, Oct 4, 3:07 PM
markj added a parent revision: D46942: vm_map: Record the maximum size of the map over time.
markj added a child revision: D46944: vm_page: Fix a logic bug in vm_page_unwire_managed().
kib accepted this revision.Fri, Oct 4, 3:31 PM
This revision is now accepted and ready to land.Fri, Oct 4, 3:31 PM
alc accepted this revision.Fri, Oct 4, 3:39 PM
dougm added inline comments.Fri, Oct 4, 4:04 PM
sys/vm/vm_page.c
5274

What about here?

markj added inline comments.Fri, Oct 4, 4:09 PM
sys/vm/vm_page.c
5274

I don't see any need to here, since the value is not used before it's passed to atomic_fcmpset. Or, in the last case in this function, it's loaded only once.

dougm accepted this revision.Fri, Oct 4, 4:33 PM

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sys/
vm/
8 lines

Diff 144250

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sys/vm/vm_page.c

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