It this the delta during one of these lockups? If so, it would seem
that although dirty pages are reported against the BDI, no actual dirty
inodes could be found.
[ note to self: writeback_inodes() seems to write out to any superblock
in the system. Might want to limit that to superblocks on wbc->bdi ]
You say that switching to .23-rc6-mm1 solved it in your case. You are
developing in the writeback_inodes() path, right? Could it be one of
your local changes that confused it here?
That is an interesting idea how about this:
---
Subject: mm: speed up writeback ramp-up on clean systems
We allow violation of bdi limits if there is a lot of room on the
system. Once we hit half the total limit we start enforcing bdi limits
and bdi ramp-up should happen. Doing it this way avoids many small
writeouts on an otherwise idle system and should also speed up the
ramp-up.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
---
Index: linux-2.6/mm/page-writeback.c
===================================================================
--- linux-2.6.orig/mm/page-writeback.c
+++ linux-2.6/mm/page-writeback.c
@@ -355,8 +355,8 @@ get_dirty_limits(long *pbackground, long
*/
static void balance_dirty_pages(struct address_space *mapping)
{
- long bdi_nr_reclaimable;
- long bdi_nr_writeback;
+ long nr_reclaimable, bdi_nr_reclaimable;
+ long nr_writeback, bdi_nr_writeback;
long background_thresh;
long dirty_thresh;
long bdi_thresh;
@@ -376,9 +376,24 @@ static void balance_dirty_pages(struct a
get_dirty_limits(&background_thresh, &dirty_thresh,
&bdi_thresh, bdi);
+
+ nr_reclaimable = global_page_state(NR_FILE_DIRTY) +
+ global_page_state(NR_UNSTABLE_NFS);
+ nr_writeback = global_page_state(NR_WRITEBACK);
+
bdi_nr_reclaimable = bdi_stat(bdi, BDI_RECLAIMABLE);
bdi_nr_writeback = bdi_stat(bdi, BDI_WRITEBACK);
- if (bdi_nr_reclaimable + bdi_nr_writeback <= bdi_thresh)
+
+ /*
+ * break out early when:
+ * - we're below the bdi limit
+ * - we're below half the total limit
+ *
+ * we let the numbers exceed the strict bdi limit if the total
+ * numbers are too low, this avoids (excessive) small writeouts.
+ */
+ if (bdi_nr_reclaimable + bdi_nr_writeback <= bdi_thresh ||
+ nr_reclaimable + nr_writeback < dirty_thresh / 2)
break;
if (!bdi->dirty_exceeded)
-
