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Test PGA_REFERENCED after calling pmap_ts_referenced(), rather than before,

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so that a reference from a concurrently destroyed mapping is observed
during the current scan.

Reviewed by:	kib, markj
MFC after:	1 week
Differential Revision:	https://reviews.freebsd.org/D16277
This commit is contained in:
Alan Cox 2018-07-15 19:25:15 +00:00
parent 7f87c0406d
commit d7aeb429a0
1 changed files with 34 additions and 23 deletions
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57
sys/vm/vm_pageout.c
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@ -793,17 +793,21 @@ recheck:
* If the page has been referenced and the object is not dead,
* reactivate or requeue the page depending on whether the
* object is mapped.
*
* Test PGA_REFERENCED after calling pmap_ts_referenced() so
* that a reference from a concurrently destroyed mapping is
* observed here and now.
*/
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);
act_delta = pmap_ts_referenced(m);
else {
KASSERT(!pmap_page_is_mapped(m),
("page %p is mapped", m));
act_delta = 0;
}
if ((m->aflags & PGA_REFERENCED) != 0) {
vm_page_aflag_clear(m, PGA_REFERENCED);
act_delta++;
}
if (act_delta != 0) {
if (object->ref_count != 0) {
@ -1215,14 +1219,11 @@ act_scan:
/*
* Check to see "how much" the page has been used.
*/
if ((m->aflags & PGA_REFERENCED) != 0) {
vm_page_aflag_clear(m, PGA_REFERENCED);
act_delta = 1;
} else
act_delta = 0;
/*
*
* Test PGA_REFERENCED after calling pmap_ts_referenced() so
* that a reference from a concurrently destroyed mapping is
* observed here and now.
*
* Perform an unsynchronized object ref count check. While
* the page lock ensures that the page is not reallocated to
* another object, in particular, one with unmanaged mappings
@ -1236,7 +1237,13 @@ act_scan:
* worst, we will deactivate and reactivate the page.
*/
if (m->object->ref_count != 0)
act_delta += pmap_ts_referenced(m);
act_delta = pmap_ts_referenced(m);
else
act_delta = 0;
if ((m->aflags & PGA_REFERENCED) != 0) {
vm_page_aflag_clear(m, PGA_REFERENCED);
act_delta++;
}
/*
* Advance or decay the act_count based on recent usage.
@ -1482,17 +1489,21 @@ recheck:
* If the page has been referenced and the object is not dead,
* reactivate or requeue the page depending on whether the
* object is mapped.
*
* Test PGA_REFERENCED after calling pmap_ts_referenced() so
* that a reference from a concurrently destroyed mapping is
* observed here and now.
*/
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 {
if (object->ref_count != 0)
act_delta = pmap_ts_referenced(m);
else {
KASSERT(!pmap_page_is_mapped(m),
("page %p is mapped", m));
act_delta = 0;
}
if ((m->aflags & PGA_REFERENCED) != 0) {
vm_page_aflag_clear(m, PGA_REFERENCED);
act_delta++;
}
if (act_delta != 0) {
if (object->ref_count != 0) {