Author: alc
Date: Tue Aug 25 01:01:25 2015
New Revision: 287121
URL: https://svnweb.freebsd.org/changeset/base/287121
Log:
Testing whether a page is dirty does not require the page lock. Moreover,
it may involve a pmap operation that iterates over the page's PV list, so
unnecessarily holding the page lock is undesirable.
MFC after: 1 week
Sponsored by: EMC / Isilon Storage Division
Modified:
head/sys/vm/vm_pageout.c
Modified: head/sys/vm/vm_pageout.c
==============================================================================
--- head/sys/vm/vm_pageout.c Mon Aug 24 23:40:36 2015 (r287120)
+++ head/sys/vm/vm_pageout.c Tue Aug 25 01:01:25 2015 (r287121)
@@ -415,10 +415,13 @@ more:
ib = 0;
break;
}
- vm_page_lock(p);
vm_page_test_dirty(p);
- if (p->dirty == 0 ||
- p->queue != PQ_INACTIVE ||
+ if (p->dirty == 0) {
+ ib = 0;
+ break;
+ }
+ vm_page_lock(p);
+ if (p->queue != PQ_INACTIVE ||
p->hold_count != 0) { /* may be undergoing I/O */
vm_page_unlock(p);
ib = 0;
@@ -442,10 +445,11 @@ more:
if ((p = vm_page_next(ps)) == NULL || vm_page_busied(p))
break;
- vm_page_lock(p);
vm_page_test_dirty(p);
- if (p->dirty == 0 ||
- p->queue != PQ_INACTIVE ||
+ if (p->dirty == 0)
+ break;
+ vm_page_lock(p);
+ if (p->queue != PQ_INACTIVE ||
p->hold_count != 0) { /* may be undergoing I/O */
vm_page_unlock(p);
break;
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