Author: jeff
Date: Tue Apr 7 02:18:52 2015
New Revision: 281184
URL: https://svnweb.freebsd.org/changeset/base/281184
Log:
- Simplify vm_pageout_scan() by introducing a new vm_pageout_clean()
function that does the locking and validation associated with cleaning
a page. This moves 150 lines of code into its own function.
- Rename vm_pageout_clean() to vm_pageout_cluster() to define what it
really does; clustering nearby pages for pageout optimization.
Reviewd by: alc, kib, kmacy
Tested by: pho (earlier version)
Sponsored by: EMC / Isilon
Modified:
head/sys/vm/vm_pageout.c
Modified: head/sys/vm/vm_pageout.c
==============================================================================
--- head/sys/vm/vm_pageout.c Tue Apr 7 01:47:36 2015 (r281183)
+++ head/sys/vm/vm_pageout.c Tue Apr 7 02:18:52 2015 (r281184)
@@ -118,7 +118,8 @@ __FBSDID("$FreeBSD$");
/* the kernel process "vm_pageout"*/
static void vm_pageout(void);
static void vm_pageout_init(void);
-static int vm_pageout_clean(vm_page_t);
+static int vm_pageout_clean(vm_page_t m);
+static int vm_pageout_cluster(vm_page_t m);
static void vm_pageout_scan(struct vm_domain *vmd, int pass);
static void vm_pageout_mightbe_oom(struct vm_domain *vmd, int pass);
@@ -347,7 +348,7 @@ vm_pageout_page_lock(vm_page_t m, vm_pag
* late and we cannot do anything that will mess with the page.
*/
static int
-vm_pageout_clean(vm_page_t m)
+vm_pageout_cluster(vm_page_t m)
{
vm_object_t object;
vm_page_t mc[2*vm_pageout_page_count], pb, ps;
@@ -906,6 +907,115 @@ vm_pageout_map_deactivate_pages(map, des
#endif /* !defined(NO_SWAPPING) */
/*
+ * Attempt to acquire all of the necessary locks to launder a page and
+ * then call through the clustering layer to PUTPAGES. Wait a short
+ * time for a vnode lock.
+ *
+ * Requires the page and object lock on entry, releases both before return.
+ * Returns 0 on success and an errno otherwise.
+ */
+static int
+vm_pageout_clean(vm_page_t m)
+{
+ struct vnode *vp;
+ struct mount *mp;
+ vm_object_t object;
+ vm_pindex_t pindex;
+ int error, lockmode;
+
+ vm_page_assert_locked(m);
+ object = m->object;
+ VM_OBJECT_ASSERT_WLOCKED(object);
+ error = 0;
+ vp = NULL;
+ mp = NULL;
+
+ /*
+ * The object is already known NOT to be dead. It
+ * is possible for the vget() to block the whole
+ * pageout daemon, but the new low-memory handling
+ * code should prevent it.
+ *
+ * We can't wait forever for the vnode lock, we might
+ * deadlock due to a vn_read() getting stuck in
+ * vm_wait while holding this vnode. We skip the
+ * vnode if we can't get it in a reasonable amount
+ * of time.
+ */
+ if (object->type == OBJT_VNODE) {
+ vm_page_unlock(m);
+ vp = object->handle;
+ if (vp->v_type == VREG &&
+ vn_start_write(vp, &mp, V_NOWAIT) != 0) {
+ mp = NULL;
+ error = EDEADLK;
+ goto unlock_all;
+ }
+ KASSERT(mp != NULL,
+ ("vp %p with NULL v_mount", vp));
+ vm_object_reference_locked(object);
+ pindex = m->pindex;
+ VM_OBJECT_WUNLOCK(object);
+ lockmode = MNT_SHARED_WRITES(vp->v_mount) ?
+ LK_SHARED : LK_EXCLUSIVE;
+ if (vget(vp, lockmode | LK_TIMELOCK, curthread)) {
+ vp = NULL;
+ error = EDEADLK;
+ goto unlock_mp;
+ }
+ VM_OBJECT_WLOCK(object);
+ vm_page_lock(m);
+ /*
+ * While the object and page were unlocked, the page
+ * may have been:
+ * (1) moved to a different queue,
+ * (2) reallocated to a different object,
+ * (3) reallocated to a different offset, or
+ * (4) cleaned.
+ */
+ if (m->queue != PQ_INACTIVE || m->object != object ||
+ m->pindex != pindex || m->dirty == 0) {
+ vm_page_unlock(m);
+ error = ENXIO;
+ goto unlock_all;
+ }
+
+ /*
+ * The page may have been busied or held while the object
+ * and page locks were released.
+ */
+ if (vm_page_busied(m) || m->hold_count != 0) {
+ vm_page_unlock(m);
+ error = EBUSY;
+ goto unlock_all;
+ }
+ }
+
+ /*
+ * If a page is dirty, then it is either being washed
+ * (but not yet cleaned) or it is still in the
+ * laundry. If it is still in the laundry, then we
+ * start the cleaning operation.
+ */
+ if (vm_pageout_cluster(m) == 0)
+ error = EIO;
+
+unlock_all:
+ VM_OBJECT_WUNLOCK(object);
+
+unlock_mp:
+ vm_page_lock_assert(m, MA_NOTOWNED);
+ if (mp != NULL) {
+ if (vp != NULL)
+ vput(vp);
+ vm_object_deallocate(object);
+ vn_finished_write(mp);
+ }
+
+ return (error);
+}
+
+/*
* vm_pageout_scan does the dirty work for the pageout daemon.
*
* pass 0 - Update active LRU/deactivate pages
@@ -921,7 +1031,6 @@ vm_pageout_scan(struct vm_domain *vmd, i
int act_delta, addl_page_shortage, deficit, maxscan, page_shortage;
int vnodes_skipped = 0;
int maxlaunder;
- int lockmode;
boolean_t queues_locked;
/*
@@ -1155,9 +1264,7 @@ vm_pageout_scan(struct vm_domain *vmd, i
* on the inactive queue, we may have to go all out.
*/
int swap_pageouts_ok;
- struct vnode *vp = NULL;
- struct mount *mp = NULL;
- vm_pindex_t pindex;
+ int error;
if ((object->type != OBJT_SWAP) && (object->type !=
OBJT_DEFAULT)) {
swap_pageouts_ok = 1;
@@ -1180,124 +1287,20 @@ vm_pageout_scan(struct vm_domain *vmd, i
vm_page_requeue_locked(m);
goto relock_queues;
}
-
+ error = vm_pageout_clean(m);
/*
- * The object is already known NOT to be dead. It
- * is possible for the vget() to block the whole
- * pageout daemon, but the new low-memory handling
- * code should prevent it.
- *
- * The previous code skipped locked vnodes and, worse,
- * reordered pages in the queue. This results in
- * completely non-deterministic operation and, on a
- * busy system, can lead to extremely non-optimal
- * pageouts. For example, it can cause clean pages
- * to be freed and dirty pages to be moved to the end
- * of the queue. Since dirty pages are also moved to
- * the end of the queue once-cleaned, this gives
- * way too large a weighting to deferring the freeing
- * of dirty pages.
- *
- * We can't wait forever for the vnode lock, we might
- * deadlock due to a vn_read() getting stuck in
- * vm_wait while holding this vnode. We skip the
- * vnode if we can't get it in a reasonable amount
- * of time.
- */
- if (object->type == OBJT_VNODE) {
- vm_page_unlock(m);
- vp = object->handle;
- if (vp->v_type == VREG &&
- vn_start_write(vp, &mp, V_NOWAIT) != 0) {
- mp = NULL;
- ++pageout_lock_miss;
- if (object->flags & OBJ_MIGHTBEDIRTY)
- vnodes_skipped++;
- goto unlock_and_continue;
- }
- KASSERT(mp != NULL,
- ("vp %p with NULL v_mount", vp));
- vm_object_reference_locked(object);
- pindex = m->pindex;
- VM_OBJECT_WUNLOCK(object);
- lockmode = MNT_SHARED_WRITES(vp->v_mount) ?
- LK_SHARED : LK_EXCLUSIVE;
- if (vget(vp, lockmode | LK_TIMELOCK,
- curthread)) {
- VM_OBJECT_WLOCK(object);
- ++pageout_lock_miss;
- if (object->flags & OBJ_MIGHTBEDIRTY)
- vnodes_skipped++;
- vp = NULL;
- goto unlock_and_continue;
- }
- VM_OBJECT_WLOCK(object);
- vm_page_lock(m);
- /*
- * While the object and page were unlocked,
- * the page may have been
- * (1) moved to a different queue,
- * (2) reallocated to a different object,
- * (3) reallocated to a different offset, or
- * (4) cleaned.
- */
- if (m->queue != PQ_INACTIVE ||
- m->object != object ||
- m->pindex != pindex ||
- m->dirty == 0) {
- vm_page_unlock(m);
- if (object->flags & OBJ_MIGHTBEDIRTY)
- vnodes_skipped++;
- goto unlock_and_continue;
- }
-
- /*
- * The page may have been busied during the
- * blocking in vget(). We don't move the
- * page back onto the end of the queue so that
- * statistics are more correct if we don't.
- */
- if (vm_page_busied(m)) {
- vm_page_unlock(m);
- addl_page_shortage++;
- goto unlock_and_continue;
- }
-
- /*
- * If the page has become held it might
- * be undergoing I/O, so skip it
- */
- if (m->hold_count != 0) {
- vm_page_unlock(m);
- addl_page_shortage++;
- if (object->flags & OBJ_MIGHTBEDIRTY)
- vnodes_skipped++;
- goto unlock_and_continue;
- }
- }
-
- /*
- * If a page is dirty, then it is either being washed
- * (but not yet cleaned) or it is still in the
- * laundry. If it is still in the laundry, then we
- * start the cleaning operation.
- *
- * decrement page_shortage on success to account for
+ * Decrement page_shortage on success to account for
* the (future) cleaned page. Otherwise we could wind
* up laundering or cleaning too many pages.
*/
- if (vm_pageout_clean(m) != 0) {
- --page_shortage;
- --maxlaunder;
- }
-unlock_and_continue:
- vm_page_lock_assert(m, MA_NOTOWNED);
- VM_OBJECT_WUNLOCK(object);
- if (mp != NULL) {
- if (vp != NULL)
- vput(vp);
- vm_object_deallocate(object);
- vn_finished_write(mp);
+ if (error == 0) {
+ page_shortage--;
+ maxlaunder--;
+ } else if (error == EDEADLK) {
+ pageout_lock_miss++;
+ vnodes_skipped++;
+ } else if (error == EBUSY) {
+ addl_page_shortage++;
}
vm_page_lock_assert(m, MA_NOTOWNED);
goto relock_queues;
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