Mel Gorman wrote on 28.11.2012 11:13:

On Tue, Nov 27, 2012 at 03:19:38PM -0800, Linus Torvalds wrote:

quoted

On Tue, Nov 27, 2012 at 2:26 PM, Johannes Weiner [off-list ref] wrote:

quoted

On Tue, Nov 27, 2012 at 05:02:36PM -0500, Rik van Riel wrote:

quoted

And the one who comes out gets to explain to me which patch(es) I
should apply, and which I should revert, if any.

Based on the reports I've seen I expect the following to work for 3.7

Keep
  96710098 mm: revert "mm: vmscan: scale number of pages reclaimed by reclaim/compaction based on failures"
  ef6c5be6 fix incorrect NR_FREE_PAGES accounting (appears like memory leak)

Revert
  82b212f4 Revert "mm: remove __GFP_NO_KSWAPD"

Merge
  mm: vmscan: fix kswapd endless loop on higher order allocation
  mm: Avoid waking kswapd for THP allocations when compaction is deferred or contended

I'll build a kernel with this combination and will give it a try. Maybe
one of those people that reported problems in
https://bugzilla.redhat.com/show_bug.cgi?id=866988 can try them, too.
There two people recently reported their problems were gone with kernels
that contained 82b212f4.

Johannes' patch should remove the necessity for __GFP_NO_KSWAPD revert but I
think we should also avoid waking kswapd for THP allocations if compaction
is deferred. Johannes' patch might mean that kswapd goes quickly go back
to sleep but it's still busy work.

Is there a way to trigger (some benchmark?) and detect (something in
/proc/vmstat ?) the problem Hannes patch tries to fix?

Background: The two main problems that got me into this discussion
vanished thx to 9671009 (mm: revert "mm: vmscan: scale number of pages
reclaimed by reclaim/compaction based on failures") and ef6c5be (fix
incorrect NR_FREE_PAGES accounting (appears like memory leak)). I
thought all my problems had gone, but after a few days of uptime
(suspended and resumed the particular machine a few times in between, as
I was using it just in the evenings) kswap now and then started
consuming nearly 100% of one cpu core for 10 to 15 seconds intervals (it
seems watching a YouTube video triggered it; and the machine was using a
little bit swap space). I just had started debugging this, but due to
some stupid mistake
(https://plus.google.com/107616711159256259828/posts/GXuhf1LTien ) then
rebooted the machine :-/ So maybe I hit the problem Hannes patch tries
to solve, but I'm not sure; and I have no easy way to verify quickly if
the proposed patch combination helps.

Thorsten

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>