From: Mel Gorman <mgorman@techsingularity.net>
To: Vlastimil Babka <vbabka@suse.cz>
Cc: Linux-MM <linux-mm@kvack.org>,
David Rientjes <rientjes@google.com>,
Andrea Arcangeli <aarcange@redhat.com>,
ying.huang@intel.com, kirill@shutemov.name,
Andrew Morton <akpm@linux-foundation.org>,
Linux List Kernel Mailing <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 25/25] mm, compaction: Do not direct compact remote memory
Date: Fri, 18 Jan 2019 14:46:01 +0000 [thread overview]
Message-ID: <20190118144601.GS27437@techsingularity.net> (raw)
In-Reply-To: <84a7b23a-1cb7-b888-4245-6b1e829f472b@suse.cz>
On Fri, Jan 18, 2019 at 02:51:00PM +0100, Vlastimil Babka wrote:
> On 1/4/19 1:50 PM, Mel Gorman wrote:
> > Remote compaction is expensive and possibly counter-productive. Locality
> > is expected to often have better performance characteristics than remote
> > high-order pages. For small allocations, it's expected that locality is
> > generally required or fallbacks are possible. For larger allocations such
> > as THP, they are forbidden at the time of writing but if __GFP_THISNODE
> > is ever removed, then it would still be preferable to fallback to small
> > local base pages over remote THP in the general case. kcompactd is still
> > woken via kswapd so compaction happens eventually.
> >
> > While this patch potentially has both positive and negative effects,
> > it is best to avoid the possibility of remote compaction given the cost
> > relative to any potential benefit.
> >
> > Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
>
> Generally agree with the intent, but what if there's e.g. high-order (but not
> costly) kernel allocation on behalf of user process on cpu belonging to a
> movable node, where the only non-movable node is node 0. It will have to keep
> reclaiming until a large enough page is formed, or wait for kcompactd?
Nnnggghhh, movable nodes. Yes, in such a case it would have to wait for
reclaim or kcompactd which could be problematic. This would have to be
special cased further.
> So maybe do this only for costly orders?
>
This was written on the basis of the __GFP_THISNODE discussion which is
THP specific so costly didn't come into my thinking. If that ever gets
resurrected properly, this patch can be revisited. It would be trivial to
check if the preferred node is a movable node and allow remote compaction
in such cases but I'm not aiming at any specific problem with this patch
so it's too hand-wavy.
> Also I think compaction_zonelist_suitable() should be also updated, or we might
> be promising the reclaim-compact loop e.g. that we will compact after enough
> reclaim, but then we won't.
>
True. I think I'll kill this patch as __GFP_THISNODE is now used again
for THP (regardless of how one feels about the subject) and we don't have
good examples where remote compaction for lower-order kernel allocations
is a problem.
--
Mel Gorman
SUSE Labs
next prev parent reply other threads:[~2019-01-18 14:46 UTC|newest]
Thread overview: 75+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-01-04 12:49 [PATCH 00/25] Increase success rates and reduce latency of compaction v2 Mel Gorman
2019-01-04 12:49 ` [PATCH 01/25] mm, compaction: Shrink compact_control Mel Gorman
2019-01-04 12:49 ` [PATCH 02/25] mm, compaction: Rearrange compact_control Mel Gorman
2019-01-04 12:49 ` [PATCH 03/25] mm, compaction: Remove last_migrated_pfn from compact_control Mel Gorman
2019-01-04 12:49 ` [PATCH 04/25] mm, compaction: Remove unnecessary zone parameter in some instances Mel Gorman
2019-01-15 11:43 ` Vlastimil Babka
2019-01-04 12:49 ` [PATCH 05/25] mm, compaction: Rename map_pages to split_map_pages Mel Gorman
2019-01-15 11:59 ` Vlastimil Babka
2019-01-04 12:49 ` [PATCH 06/25] mm, compaction: Skip pageblocks with reserved pages Mel Gorman
2019-01-15 12:10 ` Vlastimil Babka
2019-01-15 12:50 ` Mel Gorman
2019-01-16 9:42 ` Mel Gorman
2019-01-04 12:49 ` [PATCH 07/25] mm, migrate: Immediately fail migration of a page with no migration handler Mel Gorman
2019-01-04 12:49 ` [PATCH 08/25] mm, compaction: Always finish scanning of a full pageblock Mel Gorman
2019-01-04 12:49 ` [PATCH 09/25] mm, compaction: Use the page allocator bulk-free helper for lists of pages Mel Gorman
2019-01-15 12:39 ` Vlastimil Babka
2019-01-16 9:46 ` Mel Gorman
2019-01-04 12:49 ` [PATCH 10/25] mm, compaction: Ignore the fragmentation avoidance boost for isolation and compaction Mel Gorman
2019-01-15 13:18 ` Vlastimil Babka
2019-01-04 12:49 ` [PATCH 11/25] mm, compaction: Use free lists to quickly locate a migration source Mel Gorman
2019-01-16 13:15 ` Vlastimil Babka
2019-01-16 14:33 ` Mel Gorman
2019-01-16 15:00 ` Vlastimil Babka
2019-01-16 15:43 ` Mel Gorman
2019-01-04 12:49 ` [PATCH 12/25] mm, compaction: Keep migration source private to a single compaction instance Mel Gorman
2019-01-16 15:45 ` Vlastimil Babka
2019-01-16 16:15 ` Mel Gorman
2019-01-17 9:29 ` Vlastimil Babka
2019-01-17 9:40 ` Vlastimil Babka
2019-01-04 12:49 ` [PATCH 13/25] mm, compaction: Use free lists to quickly locate a migration target Mel Gorman
2019-01-17 14:36 ` Vlastimil Babka
2019-01-17 15:51 ` Mel Gorman
2019-01-04 12:50 ` [PATCH 14/25] mm, compaction: Avoid rescanning the same pageblock multiple times Mel Gorman
2019-01-17 15:16 ` Vlastimil Babka
2019-01-17 16:00 ` Mel Gorman
2019-01-04 12:50 ` [PATCH 15/25] mm, compaction: Finish pageblock scanning on contention Mel Gorman
2019-01-17 16:38 ` Vlastimil Babka
2019-01-17 17:11 ` Mel Gorman
2019-01-18 8:57 ` Vlastimil Babka
2019-01-04 12:50 ` [PATCH 16/25] mm, compaction: Check early for huge pages encountered by the migration scanner Mel Gorman
2019-01-17 17:01 ` Vlastimil Babka
2019-01-17 17:35 ` Mel Gorman
2019-01-04 12:50 ` [PATCH 17/25] mm, compaction: Keep cached migration PFNs synced for unusable pageblocks Mel Gorman
2019-01-17 17:17 ` Vlastimil Babka
2019-01-17 17:37 ` Mel Gorman
2019-01-04 12:50 ` [PATCH 18/25] mm, compaction: Rework compact_should_abort as compact_check_resched Mel Gorman
2019-01-17 17:27 ` Vlastimil Babka
2019-01-04 12:50 ` [PATCH 19/25] mm, compaction: Do not consider a need to reschedule as contention Mel Gorman
2019-01-17 17:33 ` Vlastimil Babka
2019-01-17 18:05 ` Mel Gorman
2019-01-04 12:50 ` [PATCH 20/25] mm, compaction: Reduce unnecessary skipping of migration target scanner Mel Gorman
2019-01-17 17:58 ` Vlastimil Babka
2019-01-17 19:39 ` Mel Gorman
2019-01-18 9:09 ` Vlastimil Babka
2019-01-04 12:50 ` [PATCH 21/25] mm, compaction: Round-robin the order while searching the free lists for a target Mel Gorman
2019-01-18 9:17 ` Vlastimil Babka
2019-01-04 12:50 ` [PATCH 22/25] mm, compaction: Sample pageblocks for free pages Mel Gorman
2019-01-18 10:38 ` Vlastimil Babka
2019-01-18 13:44 ` Mel Gorman
2019-01-04 12:50 ` [PATCH 23/25] mm, compaction: Be selective about what pageblocks to clear skip hints Mel Gorman
2019-01-18 12:55 ` Vlastimil Babka
2019-01-18 14:10 ` Mel Gorman
2019-01-04 12:50 ` [PATCH 24/25] mm, compaction: Capture a page under direct compaction Mel Gorman
2019-01-18 13:40 ` Vlastimil Babka
2019-01-18 14:39 ` Mel Gorman
2019-01-04 12:50 ` [PATCH 25/25] mm, compaction: Do not direct compact remote memory Mel Gorman
2019-01-18 13:51 ` Vlastimil Babka
2019-01-18 14:46 ` Mel Gorman [this message]
2019-01-07 23:43 ` [PATCH 00/25] Increase success rates and reduce latency of compaction v2 Andrew Morton
2019-01-08 9:12 ` Mel Gorman
2019-01-09 11:13 ` [PATCH] mm, compaction: Use free lists to quickly locate a migration target -fix Mel Gorman
2019-01-09 19:27 ` Andrew Morton
2019-01-09 21:26 ` Mel Gorman
2019-01-09 11:15 ` [PATCH] mm, compaction: Finish pageblock scanning on contention -fix Mel Gorman
2019-01-09 11:16 ` [PATCH] mm, compaction: Round-robin the order while searching the free lists for a target -fix Mel Gorman
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