On Wed, May 05, 2010 at 01:51:56PM +0100, Mel Gorman wrote:
> On Wed, May 05, 2010 at 02:19:08PM +0200, Andrea Arcangeli wrote:
> > On Tue, Apr 20, 2010 at 10:01:14PM +0100, Mel Gorman wrote:
> > > + if (page) {
> > > + __count_vm_event(COMPACTSUCCESS);
> > > + return page;
> >
> > ==
> > From: Andrea Arcangeli <aarcange@xxxxxxxxxx>
> >
> > Preempt is enabled so it must use count_vm_event.
> >
> > Signed-off-by: Andrea Arcangeli <aarcange@xxxxxxxxxx>
>
> Reviewed-by: Mel Gorman <mel@xxxxxxxxx>
>
> Andrew, this is a fix to the patch
> mmcompaction-direct-compact-when-a-high-order-allocation-fails.patch
for Andrew: I'll generate a trivial reject to the exponential backoff.
> Thanks Andrea, well spotted.
You're welcome.
I updated current aa.git origin/master and origin/anon_vma_chain
branches (post THP-23*).
There's also another patch I've in my tree that you didn't picked up
and I wonder what's the issue here. This less a bugfix because it
seems to only affect lockdep, I don't know why lockdep forbids to call
migrate_prep with any lock held (in this case the mmap_sem). migrate.c
is careful to comply with it, compaction.c isn't. It's not mandatory
to succeed for compaction, so in doubt I just commented it out. It'll
also decrease the IPI load so I wasn't very concerned to re-enable it.
-----
Subject: disable migrate_prep()
From: Andrea Arcangeli <aarcange@xxxxxxxxxx>
I get trouble from lockdep if I leave it enabled:
=======================================================
[ INFO: possible circular locking dependency detected ]
2.6.34-rc3 #50
-------------------------------------------------------
largepages/4965 is trying to acquire lock:
(events){+.+.+.}, at: [<ffffffff8105b788>] flush_work+0x38/0x130
but task is already holding lock:
(&mm->mmap_sem){++++++}, at: [<ffffffff8141b022>] do_page_fault+0xd2/0x430
flush_work apparently wants to run free from lock and it bugs in:
lock_map_acquire(&cwq->wq->lockdep_map);
Signed-off-by: Andrea Arcangeli <aarcange@xxxxxxxxxx>
---
diff --git a/mm/compaction.c b/mm/compaction.c
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -383,7 +383,9 @@ static int compact_zone(struct zone *zon
cc->free_pfn = cc->migrate_pfn + zone->spanned_pages;
cc->free_pfn &= ~(pageblock_nr_pages-1);
+#if 0
migrate_prep();
+#endif
while ((ret = compact_finished(zone, cc)) == COMPACT_CONTINUE) {
unsigned long nr_migrate, nr_remaining;
--
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