Author: alc
Date: Sat Jan 18 20:02:59 2014
New Revision: 260859
URL: http://svnweb.freebsd.org/changeset/base/260859
Log:
Style changes in vm_pageout_scan():
1. Be consistent in the style of "act_delta" manipulations between the
inactive and active queue scans.
2. Explicitly compare to zero.
3. The deactivation of a page is based is based on its recent history
and not just the current call to vm_pageout_scan(). The variable
"act_delta" represents the current state of the page, and not its
history. Avoid possible confusion by not (ab)using "act_delta" for
the making the deactivation decision.
Submitted by: kib [1]
Reviewed by: kib [2,3]
Modified:
head/sys/vm/vm_pageout.c
Modified: head/sys/vm/vm_pageout.c
==============================================================================
--- head/sys/vm/vm_pageout.c Sat Jan 18 18:41:24 2014 (r260858)
+++ head/sys/vm/vm_pageout.c Sat Jan 18 20:02:59 2014 (r260859)
@@ -1047,11 +1047,11 @@ vm_pageout_scan(struct vm_domain *vmd, i
* level VM system not knowing anything about existing
* references.
*/
- act_delta = 0;
if ((m->aflags & PGA_REFERENCED) != 0) {
vm_page_aflag_clear(m, PGA_REFERENCED);
act_delta = 1;
- }
+ } else
+ act_delta = 0;
if (object->ref_count != 0) {
act_delta += pmap_ts_referenced(m);
} else {
@@ -1064,7 +1064,7 @@ vm_pageout_scan(struct vm_domain *vmd, i
* references, we reactivate the page or requeue it.
*/
if (act_delta != 0) {
- if (object->ref_count) {
+ if (object->ref_count != 0) {
vm_page_activate(m);
m->act_count += act_delta + ACT_ADVANCE;
} else {
@@ -1361,11 +1361,12 @@ relock_queues:
/*
* Check to see "how much" the page has been used.
*/
- act_delta = 0;
- if (m->aflags & PGA_REFERENCED) {
+ if ((m->aflags & PGA_REFERENCED) != 0) {
vm_page_aflag_clear(m, PGA_REFERENCED);
- act_delta += 1;
- }
+ act_delta = 1;
+ } else
+ act_delta = 0;
+
/*
* Unlocked object ref count check. Two races are possible.
* 1) The ref was transitioning to zero and we saw non-zero,
@@ -1380,20 +1381,18 @@ relock_queues:
/*
* Advance or decay the act_count based on recent usage.
*/
- if (act_delta) {
+ if (act_delta != 0) {
m->act_count += ACT_ADVANCE + act_delta;
if (m->act_count > ACT_MAX)
m->act_count = ACT_MAX;
- } else {
+ } else
m->act_count -= min(m->act_count, ACT_DECLINE);
- act_delta = m->act_count;
- }
/*
* Move this page to the tail of the active or inactive
* queue depending on usage.
*/
- if (act_delta == 0) {
+ if (m->act_count == 0) {
/* Dequeue to avoid later lock recursion. */
vm_page_dequeue_locked(m);
vm_page_deactivate(m);
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