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Modify dirty page purging algorithm.

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Convert chunks_dirty from a red-black tree to a doubly linked list,
and use it to purge dirty pages from chunks in FIFO order.

Add a lock around the code that purges dirty pages via madvise(2), in
order to avoid kernel contention.  If lock acquisition fails,
indefinitely postpone purging dirty pages.

Add a lower limit of one chunk worth of dirty pages per arena for
purging, in addition to the active:dirty ratio.

When purging, purge all dirty pages from at least one chunk, but rather
than purging enough pages to drop to half the purging threshold, merely
drop to the threshold.
This commit is contained in:
Jason Evans
2010-03-04 21:35:07 -08:00
parent 3c2d9c899c
commit 2caa4715ed
4 changed files with 80 additions and 75 deletions
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5
jemalloc/doc/jemalloc.3.in
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@@ -38,7 +38,7 @@
.\" @(#)malloc.3 8.1 (Berkeley) 6/4/93
.\" $FreeBSD: head/lib/libc/stdlib/malloc.3 182225 2008-08-27 02:00:53Z jasone $
.\"
.Dd March 1, 2010
.Dd March 4, 2010
.Dt JEMALLOC 3
.Os
.Sh NAME
@@ -333,7 +333,8 @@ The default value is 512 bytes.
.It D
Halve/double the per-arena minimum ratio of active to dirty pages.
Some dirty unused pages may be allowed to accumulate, within the limit set by
the ratio, before informing the kernel about at least half of those pages via
the ratio (or one chunk worth of dirty pages, whichever is greater), before
informing the kernel about some of those pages via
.Xr madvise 2 .
This provides the kernel with sufficient information to recycle dirty pages if
physical memory becomes scarce and the pages remain unused.