|author||Konstantin Belousov <kib@FreeBSD.org>||2019-09-04 20:28:16 +0000|
|committer||Konstantin Belousov <kib@FreeBSD.org>||2019-09-04 20:28:16 +0000|
madvise(MADV_FREE): Quick fix to time rewind.
Don't free pages in a shadowing object. While this degrades MADV_FREE to a no-op (and we could, instead, choose to fall back to MADV_DONTNEED, at the cost of changing pmap_madvise), this is presently considered a temporary fix. We may prefer to risk a little fragmentation of the map by creating a zero/OBJT_DEFAULT entry over top of the existing object and, simultaneously, revert to the existing marking any pages in the former shadowing object in the advised region as reclaimable. At least one consumer of MADV_FREE (snmalloc) may use mmap() to construct zeroed pages "eventually" here anyway, so the fragmentation may be coming anyway. Submitted by: Nathaniel Filardo <firstname.lastname@example.org> PR: 240061 Reviewed by: markj MFC after: 1 week Differential revision: https://reviews.freebsd.org/D21517
Notes: svn path=/head/; revision=351830
Diffstat (limited to 'stand')
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