Date: Sat, 10 Jul 2010 18:22:44 +0000 (UTC) From: Alan Cox <alc@FreeBSD.org> To: cvs-src-old@freebsd.org Subject: cvs commit: src/sys/amd64/amd64 pmap.c src/sys/i386/i386 pmap.c Message-ID: <201007101824.o6AIO1qc085971@repoman.freebsd.org>
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alc 2010-07-10 18:22:44 UTC
FreeBSD src repository
Modified files:
sys/amd64/amd64 pmap.c
sys/i386/i386 pmap.c
Log:
SVN rev 209887 on 2010-07-10 18:22:44Z by alc
Reduce the number of global TLB shootdowns generated by pmap_qenter().
Specifically, teach pmap_qenter() to recognize the case when it is being
asked to replace a mapping with the very same mapping and not generate
a shootdown. Unfortunately, the buffer cache commonly passes an entire
buffer to pmap_qenter() when only a subset of the mappings are changing.
For the extension of buffers in allocbuf() this was resulting in
unnecessary shootdowns. The addition of new pages to the end of the
buffer need not and did not trigger a shootdown, but overwriting the
initial mappings with the very same mappings was seen as a change that
necessitated a shootdown. With this change, that is no longer so.
For a "buildworld" on amd64, this change eliminates 14-15% of the
pmap_invalidate_range() shootdowns, and about 4% of the overall
shootdowns.
MFC after: 3 weeks
Revision Changes Path
1.708 +9 -6 src/sys/amd64/amd64/pmap.c
1.688 +9 -6 src/sys/i386/i386/pmap.c
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