Messages in this thread Patch in this message | | | Date | Wed, 5 May 2010 15:11:12 +0200 | From | Andrea Arcangeli <> | Subject | Re: [PATCH] fix count_vm_event preempt in memory compaction direct reclaim |
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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@redhat.com> > > > > Preempt is enabled so it must use count_vm_event. > > > > Signed-off-by: Andrea Arcangeli <aarcange@redhat.com> > > Reviewed-by: Mel Gorman <mel@csn.ul.ie> > > 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@redhat.com>
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@redhat.com> ---
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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