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Code Issues Releases Activity

Style changes in vm_pageout_scan():

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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]
This commit is contained in:
Alan Cox 2014-01-18 20:02:59 +00:00
parent b6a16fc853
commit 86fa24710e
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=260859
1 changed files with 11 additions and 12 deletions
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23
sys/vm/vm_pageout.c
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@ -1047,11 +1047,11 @@ vm_pageout_scan(struct vm_domain *vmd, int pass)
* 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, int pass)
* 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 @@ vm_pageout_scan(struct vm_domain *vmd, int pass)
/*
* 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 @@ vm_pageout_scan(struct vm_domain *vmd, int pass)
/*
* 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);