A pair of UMA optimizations to improve cache behavior.
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Authored by jeff on Feb 24 2020, 11:26 PM.

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rlibby
markj

Commits

rS358377: A pair of performance improvements.

Summary

This adds a missing swap to uma_zfree to protect lifo behavior. The alloc bucket is now always the most recent data. This was +8% on my test.

It changes the load balancing algorithm for ROUNDROBIN to more strongly prefer the current domain unless there is a severe imbalance. I don't recall the actual % gain but it was not insignificant.

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Buildable 29584
Build 27445: arc lint + arc unit

Event Timeline

jeff created this revision.Feb 24 2020, 11:26 PM

Harbormaster completed remote builds in B29584: Diff 68779.Feb 24 2020, 11:26 PM

jeff edited the summary of this revision. (Show Details)Feb 24 2020, 11:39 PM

jeff added reviewers: rlibby, markj.

jeff set the repository for this revision to rS FreeBSD src repository - subversion.

Herald added a subscriber: imp. · View Herald TranscriptFeb 24 2020, 11:39 PM

markj added inline comments.Feb 25 2020, 1:52 AM

sys/vm/uma_core.c
586	Style: missing spaces around '*'.
587	Suppose we have domains 0, 1 with 100 and 99 items, respectively, and pref == 0. Then prefitems is left equal to LONG_MAX and we will return domain 1, but it looks like the intent is to return 0 in this case.