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Index: head/sys/kern/vfs_bio.c
===================================================================
--- head/sys/kern/vfs_bio.c
+++ head/sys/kern/vfs_bio.c
@@ -2901,7 +2901,8 @@
}
/*
- * Unwire a page held by a buf and place it on the appropriate vm queue.
+ * Unwire a page held by a buf and either free it or update the page queues to
+ * reflect its recent use.
*/
static void
vfs_vmio_unwire(struct buf *bp, vm_page_t m)
@@ -2910,24 +2911,26 @@
vm_page_lock(m);
if (vm_page_unwire_noq(m)) {
- /*
- * Determine if the page should be freed before adding
- * it to the inactive queue.
- */
- if (m->valid == 0) {
- freed = !vm_page_busied(m);
- if (freed)
- vm_page_free(m);
- } else if ((bp->b_flags & B_DIRECT) != 0)
+ if ((bp->b_flags & B_DIRECT) != 0)
freed = vm_page_try_to_free(m);
else
freed = false;
if (!freed) {
/*
- * If the page is unlikely to be reused, let the
- * VM know. Otherwise, maintain LRU.
+ * Use a racy check of the valid bits to determine
+ * whether we can accelerate reclamation of the page.
+ * The valid bits will be stable unless the page is
+ * being mapped or is referenced by multiple buffers,
+ * and in those cases we expect races to be rare. At
+ * worst we will either accelerate reclamation of a
+ * valid page and violate LRU, or unnecessarily defer
+ * reclamation of an invalid page.
+ *
+ * The B_NOREUSE flag marks data that is not expected to
+ * be reused, so accelerate reclamation in that case
+ * too. Otherwise, maintain LRU.
*/
- if ((bp->b_flags & B_NOREUSE) != 0)
+ if (m->valid == 0 || (bp->b_flags & B_NOREUSE) != 0)
vm_page_deactivate_noreuse(m);
else if (m->queue == PQ_ACTIVE)
vm_page_reference(m);
@@ -3014,7 +3017,11 @@
(desiredpages << PAGE_SHIFT), bp->b_npages - desiredpages);
} else
BUF_CHECK_UNMAPPED(bp);
- obj = bp->b_bufobj->bo_object;
+
+ /*
+ * The object lock is needed only if we will attempt to free pages.
+ */
+ obj = (bp->b_flags & B_DIRECT) != 0 ? bp->b_bufobj->bo_object : NULL;
if (obj != NULL)
VM_OBJECT_WLOCK(obj);
for (i = desiredpages; i < bp->b_npages; i++) {

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