Author: markj
Date: Mon Aug 26 20:20:10 2019
New Revision: 351518
URL: https://svnweb.freebsd.org/changeset/base/351518
Log:
Fix a few nits in vm_pqbatch_process_page().
- Don't bother masking off non-queue state flags when loading the
page's atomic state, since it is only required for one of the
function's assertions. Update the assertion instead.
- Remove an incorrect comment regarding synchronization with the
page daemon. The page daemon only ever checks for PGA_ENQUEUED
with the page queue lock held.
- When clearing requeue flags, only clear the flags that have been
acted upon.
Reviewed by: kib (previous version)
Discussed with: alc
Tested by: pho (part of a larger patch)
MFC after: 1 week
Sponsored by: Netflix
Differential Revision: https://reviews.freebsd.org/D21368
Modified:
head/sys/vm/vm_page.c
Modified: head/sys/vm/vm_page.c
==============================================================================
--- head/sys/vm/vm_page.c Mon Aug 26 18:57:29 2019 (r351517)
+++ head/sys/vm/vm_page.c Mon Aug 26 20:20:10 2019 (r351518)
@@ -3081,9 +3081,10 @@ vm_pqbatch_process_page(struct vm_pagequeue *pq, vm_pa
* the page queue lock held. In this case it is about to free the page,
* which must not have any queue state.
*/
- qflags = atomic_load_8(&m->aflags) & PGA_QUEUE_STATE_MASK;
- KASSERT(pq == vm_page_pagequeue(m) || qflags == 0,
- ("page %p doesn't belong to queue %p but has queue state %#x",
+ qflags = atomic_load_8(&m->aflags);
+ KASSERT(pq == vm_page_pagequeue(m) ||
+ (qflags & PGA_QUEUE_STATE_MASK) == 0,
+ ("page %p doesn't belong to queue %p but has aflags %#x",
m, pq, qflags));
if ((qflags & PGA_DEQUEUE) != 0) {
@@ -3097,6 +3098,13 @@ vm_pqbatch_process_page(struct vm_pagequeue *pq, vm_pa
vm_pagequeue_cnt_inc(pq);
vm_page_aflag_set(m, PGA_ENQUEUED);
}
+
+ /*
+ * Give PGA_REQUEUE_HEAD precedence over PGA_REQUEUE.
+ * In particular, if both flags are set in close succession,
+ * only PGA_REQUEUE_HEAD will be applied, even if it was set
+ * first.
+ */
if ((qflags & PGA_REQUEUE_HEAD) != 0) {
KASSERT(m->queue == PQ_INACTIVE,
("head enqueue not supported for page %p", m));
@@ -3105,12 +3113,8 @@ vm_pqbatch_process_page(struct vm_pagequeue *pq, vm_pa
} else
TAILQ_INSERT_TAIL(&pq->pq_pl, m, plinks.q);
- /*
- * PGA_REQUEUE and PGA_REQUEUE_HEAD must be cleared after
- * setting PGA_ENQUEUED in order to synchronize with the
- * page daemon.
- */
- vm_page_aflag_clear(m, PGA_REQUEUE | PGA_REQUEUE_HEAD);
+ vm_page_aflag_clear(m, qflags & (PGA_REQUEUE |
+ PGA_REQUEUE_HEAD));
}
}
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