iommu_gas: change to first-fit search for lowermatch
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Authored by dougm on Jun 12 2022, 10:38 PM.

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alc
kib

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rG9b12e43d1f80: iommu_gas: use to first-fit search for lowermatch
rG975715b78819: iommu_gas: use to first-fit search for lowermatch

Summary

Reverse the order of the search for a free space in lowermatch, to make it a first-fit search. Iommu_gas_match_one always allocates from the beginning of the free gap discovered from searching the tree, so the current code isn't really allocating in a reverse first-fit anyway, and making the search first-fit reduces the number of iommu page table pages that are used.

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rG FreeBSD src repository

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Event Timeline

dougm requested review of this revision.Jun 12 2022, 10:38 PM

dougm created this revision.

Please explain why this change is needed in the summary.

This revision is now accepted and ready to land.Jun 13 2022, 6:19 AM

dougm edited the summary of this revision. (Show Details)Jun 13 2022, 8:30 AM

For posterity, in other words, anyone who looks at this review, this change together with the last two changes to this same file have reduced iommu page table page usage by a netperf TCP_MAERTS test from ~181 to ~151.

dougm edited the summary of this revision. (Show Details)Jun 13 2022, 5:29 PM

dougm added a reviewer: kib.

kib accepted this revision.Jun 14 2022, 5:23 AM

Closed by commit rG975715b78819: iommu_gas: use to first-fit search for lowermatch (authored by dougm). · Explain WhyJun 14 2022, 5:52 AM

This revision was automatically updated to reflect the committed changes.

dougm added a commit: rG975715b78819: iommu_gas: use to first-fit search for lowermatch.

Herald added a subscriber: imp. · View Herald TranscriptJun 14 2022, 5:52 AM

dougm added a commit: rG9b12e43d1f80: iommu_gas: use to first-fit search for lowermatch.Jul 6 2022, 5:05 PM