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The intention of r254304 was to scan the active queue continuously.

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However, I've observed the active queue scan stopping when there are
frequent free page shortages and the inactive queue is steadily refilled
by other mechanisms, such as the sequential access heuristic in vm_fault()
or madvise(2).  To remedy this problem, record the time of the last active
queue scan, and always scan a number of pages proportional to the time
since the last scan, regardless of whether that last scan was a
timeout-triggered ("pass == 0") or free-page-shortage-triggered ("pass >
0") scan.

Also, on a timeout-triggered scan, allow a full scan of the active queue
when the system is short of inactive pages.

Reviewed by:	kib
MFC after:	6 weeks
Sponsored by:	EMC / Isilon Storage Division
This commit is contained in:
Alan Cox 2015-07-08 17:45:59 +00:00
parent 613ab60283
commit 22cf98d1f3
2 changed files with 20 additions and 15 deletions
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1
sys/vm/vm_page.h
View File

@ -227,6 +227,7 @@ struct vm_domain {
long vmd_segs; /* bitmask of the segments */
boolean_t vmd_oom;
int vmd_pass; /* local pagedaemon pass */
int vmd_last_active_scan;
struct vm_page vmd_marker; /* marker for pagedaemon private use */
};

34
sys/vm/vm_pageout.c
View File

@ -1028,9 +1028,10 @@ vm_pageout_scan(struct vm_domain *vmd, int pass)
vm_page_t m, next;
struct vm_pagequeue *pq;
vm_object_t object;
long min_scan;
int act_delta, addl_page_shortage, deficit, maxscan, page_shortage;
int vnodes_skipped = 0;
int maxlaunder;
int maxlaunder, scan_tick, scanned;
boolean_t queues_locked;
/*
@ -1351,34 +1352,37 @@ relock_queues:
* If we're just idle polling attempt to visit every
* active page within 'update_period' seconds.
*/
if (pass == 0 && vm_pageout_update_period != 0) {
maxscan /= vm_pageout_update_period;
page_shortage = maxscan;
}
scan_tick = ticks;
if (vm_pageout_update_period != 0) {
min_scan = pq->pq_cnt;
min_scan *= scan_tick - vmd->vmd_last_active_scan;
min_scan /= hz * vm_pageout_update_period;
} else
min_scan = 0;
if (min_scan > 0 || (page_shortage > 0 && maxscan > 0))
vmd->vmd_last_active_scan = scan_tick;
/*
* Scan the active queue for things we can deactivate. We nominally
* track the per-page activity counter and use it to locate
* deactivation candidates.
* Scan the active queue for pages that can be deactivated. Update
* the per-page activity counter and use it to identify deactivation
* candidates.
*/
m = TAILQ_FIRST(&pq->pq_pl);
while (m != NULL && maxscan-- > 0 && page_shortage > 0) {
for (m = TAILQ_FIRST(&pq->pq_pl), scanned = 0; m != NULL && (scanned <
min_scan || (page_shortage > 0 && scanned < maxscan)); m = next,
scanned++) {
KASSERT(m->queue == PQ_ACTIVE,
("vm_pageout_scan: page %p isn't active", m));
next = TAILQ_NEXT(m, plinks.q);
if ((m->flags & PG_MARKER) != 0) {
m = next;
if ((m->flags & PG_MARKER) != 0)
continue;
}
KASSERT((m->flags & PG_FICTITIOUS) == 0,
("Fictitious page %p cannot be in active queue", m));
KASSERT((m->oflags & VPO_UNMANAGED) == 0,
("Unmanaged page %p cannot be in active queue", m));
if (!vm_pageout_page_lock(m, &next)) {
vm_page_unlock(m);
m = next;
continue;
}
@ -1430,7 +1434,6 @@ relock_queues:
} else
vm_page_requeue_locked(m);
vm_page_unlock(m);
m = next;
}
vm_pagequeue_unlock(pq);
#if !defined(NO_SWAPPING)
@ -1620,6 +1623,7 @@ vm_pageout_worker(void *arg)
*/
KASSERT(domain->vmd_segs != 0, ("domain without segments"));
domain->vmd_last_active_scan = ticks;
vm_pageout_init_marker(&domain->vmd_marker, PQ_INACTIVE);
/*