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As the next step in eliminating PG_CACHE pages, free rather than cache

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pages in vm_pageout_scan().  The reactivation rate of cache pages created
by vm_pageout_scan() is extremely low; typically no more than 0.5% to
2.25% of the pages are ever reactivated.  At the same time, caching pages
is more expensive than freeing them.  For example, in a test with
PostgreSQL, this change reduced the amount of time spent in the inactive
queue scan by 1/6.

Differential Revision:	https://reviews.freebsd.org/D2805
Reviewed by:	kib
Sponsored by:	EMC / Isilon Storage Division
This commit is contained in:
Alan Cox 2015-06-14 05:23:39 +00:00
parent d5e71581dd
commit 78afdce6af
1 changed files with 3 additions and 3 deletions
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6
sys/vm/vm_pageout.c
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@ -1233,10 +1233,10 @@ vm_pageout_scan(struct vm_domain *vmd, int pass)
--page_shortage;
} else if (m->dirty == 0) {
/*
* Clean pages can be placed onto the cache queue.
* This effectively frees them.
* Clean pages can be freed.
*/
vm_page_cache(m);
vm_page_free(m);
PCPU_INC(cnt.v_dfree);
--page_shortage;
} else if ((m->flags & PG_WINATCFLS) == 0 && pass < 2) {
/*