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Purging half of the spare memory, rather than just enough to get under the limit, so that there aren’t many small unmaps, and many scans for spare pages.

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 Change: 184326
 ServerID: perforce.ravenbrook.com
This commit is contained in:
Richard Brooksby 2014-02-11 18:26:00 +00:00
parent 9e057d1bcc
commit e59678ecf9
1 changed files with 11 additions and 2 deletions
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13
mps/code/arenavm.c
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@ -1296,6 +1296,8 @@ static void tablePagesUnmap(VMChunk vmChunk, Index basePage, Index limitPage)
/* Lower basePage until we reach a desciptor we can't unmap, or the
beginning of the table. */
/* FIXME: Are the descriptors below chunk->allocBase initialised? Shouldn't
we stop there? pageTable[allocBase] might cross a page boundary. */
AVER(pageState(vmChunk, basePage) == PageStateFREE);
while (basePage > 0) {
Bool mapped = pageDescIsMapped(vmChunk, basePage - 1);
@ -1714,8 +1716,15 @@ static void VMFree(Addr base, Size size, Pool pool)
/* Consider returning memory to the OS. */
/* TODO: Chunks are only destroyed when ArenaCompact is called, and that is
only called from TraceReclaim. Should consider destroying chunks here. */
if (arena->spareCommitted > arena->spareCommitLimit)
(void)VMPurgeSpare(arena, arena->spareCommitted - arena->spareCommitLimit);
if (arena->spareCommitted > arena->spareCommitLimit) {
/* Purge half of the spare memory, not just the extra sliver, so
that we return a reasonable amount of memory in one go, and avoid
lots of small unmappings, each of which has an overhead. */
/* TODO: Consider making this time-based. */
/* TODO: Consider making this smarter about the overheads tradeoff. */
Size toPurge = arena->spareCommitted - arena->spareCommitLimit / 2;
(void)VMPurgeSpare(arena, toPurge);
}
}