Differential D21115

Improve superpage handling in pmap_advise()
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Authored by alc on Jul 30 2019, 4:07 PM.

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kib
markj
manu

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rS350463: In pmap_advise(), when we encounter a superpage mapping, we first demote the

Summary

In pmap_advise(), when we encounter a superpage mapping, we first demote the mapping and then destroy one of the 4 KB page mappings so that there is a potential trigger for repromotion. Currently, we destroy the first 4 KB page mapping that falls within the (current) superpage mapping or the virtual address range {sva, eva). However, I have found empirically that destroying the last 4 KB mapping produces slightly better results, specifically, more promotions and fewer failed promotion attempts. Accordingly, this revision changes pmap_advise() to destroy the last 4 KB page mapping. It also replaces some nearby uses of boolean_t with bool.

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rS FreeBSD src repository - subversion

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Event Timeline

alc created this revision.Jul 30 2019, 4:07 PM

Herald added subscribers: emaste, andrew. · View Herald TranscriptJul 30 2019, 4:07 PM

Add context.

markj added inline comments.Jul 30 2019, 4:35 PM

amd64/amd64/pmap.c
7510 ↗	(On Diff #60294)	Should this comment be amended to explain why we choose the last page in the range?

kib accepted this revision.Jul 30 2019, 7:32 PM

This revision is now accepted and ready to land.Jul 30 2019, 7:32 PM

alc added inline comments.Jul 30 2019, 9:57 PM

amd64/amd64/pmap.c
7510 ↗	(On Diff #60294)	Yes, I will do so this evening.

markj accepted this revision.Jul 30 2019, 10:51 PM

Closed by commit rS350463: In pmap_advise(), when we encounter a superpage mapping, we first demote the (authored by alc). · Explain WhyJul 31 2019, 5:38 AM

This revision was automatically updated to reflect the committed changes.

alc added a commit: rS350463: In pmap_advise(), when we encounter a superpage mapping, we first demote the.

Herald added a reviewer: manu. · View Herald TranscriptJul 31 2019, 5:38 AM

Herald added a subscriber: imp. · View Herald Transcript

Revision Contents
Changeset List

Path

Size

head/

sys/

amd64/

amd64/

26 lines

arm64/

arm64/

18 lines

i386/

i386/

32 lines

Diff 60317

head/sys/amd64/amd64/pmap.c

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head/sys/arm64/arm64/pmap.c

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head/sys/i386/i386/pmap.c

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