linux-kernel - Re: [PATCH 2/4] mm, compaction: more reliably increase direct compaction priority

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Date:   Thu, 22 Sep 2016 17:06:36 +0200
From:   Vlastimil Babka <vbabka@...e.cz>
To:     Michal Hocko <mhocko@...nel.org>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Arkadiusz Miskiewicz <a.miskiewicz@...il.com>,
        Ralf-Peter Rohbeck <Ralf-Peter.Rohbeck@...ntum.com>,
        Olaf Hering <olaf@...fle.de>, linux-kernel@...r.kernel.org,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        linux-mm@...ck.org, Mel Gorman <mgorman@...hsingularity.net>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        David Rientjes <rientjes@...gle.com>,
        Rik van Riel <riel@...hat.com>
Subject: Re: [PATCH 2/4] mm, compaction: more reliably increase direct
 compaction priority

On 09/22/2016 04:52 PM, Michal Hocko wrote:
> On Thu 22-09-16 16:08:21, Michal Hocko wrote:
>> On Thu 22-09-16 14:51:48, Vlastimil Babka wrote:
>> > >From 465e1bd61b7a6d6901a44f09b1a76514dbc220fa Mon Sep 17 00:00:00 2001
>> > From: Vlastimil Babka <vbabka@...e.cz>
>> > Date: Thu, 22 Sep 2016 13:54:32 +0200
>> > Subject: [PATCH] mm, compaction: more reliably increase direct compaction
>> >  priority-fix
>> > 
>> > When increasing the compaction priority, also reset retries. Otherwise we can
>> > consume all retries on the lower priorities.
>> 
>> OK, this is an improvement. I am just thinking that we might want to
>> pull
>> 	if (order && compaction_made_progress(compact_result))
>> 		compaction_retries++;
>> 
>> into should_compact_retry as well. I've had it there originally because
>> it was in line with no_progress_loops but now that we have compaction
>> priorities it would fit into retry logic better. As a plus it would
>> count only those compaction rounds where we we didn't have to rely on
>                                                  did that should be
> 
>> the compaction retry logic. What do you think?

In that case I would also add this for consistency?

----8<----
>From a7921e57ba1189b9c08fc4879358a908c390e47c Mon Sep 17 00:00:00 2001
From: Vlastimil Babka <vbabka@...e.cz>
Date: Thu, 22 Sep 2016 17:02:37 +0200
Subject: [PATCH] mm, page_alloc: pull no_progress_loops update to
 should_reclaim_retry()

The should_reclaim_retry() makes decisions based on no_progress_loops, so it
makes sense to also update the counter there. It will be also consistent with
should_compact_retry() and compaction_retries. No functional change.

Signed-off-by: Vlastimil Babka <vbabka@...e.cz>
---
 mm/page_alloc.c | 28 ++++++++++++++--------------
 1 file changed, 14 insertions(+), 14 deletions(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 582820080601..a01359ab3ed6 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -3401,16 +3401,26 @@ bool gfp_pfmemalloc_allowed(gfp_t gfp_mask)
 static inline bool
 should_reclaim_retry(gfp_t gfp_mask, unsigned order,
 		     struct alloc_context *ac, int alloc_flags,
-		     bool did_some_progress, int no_progress_loops)
+		     bool did_some_progress, int *no_progress_loops)
 {
 	struct zone *zone;
 	struct zoneref *z;
 
 	/*
+	 * Costly allocations might have made a progress but this doesn't mean
+	 * their order will become available due to high fragmentation so
+	 * always increment the no progress counter for them
+	 */
+	if (did_some_progress && order <= PAGE_ALLOC_COSTLY_ORDER)
+		no_progress_loops = 0;
+	else
+		no_progress_loops++;
+
+	/*
 	 * Make sure we converge to OOM if we cannot make any progress
 	 * several times in the row.
 	 */
-	if (no_progress_loops > MAX_RECLAIM_RETRIES)
+	if (*no_progress_loops > MAX_RECLAIM_RETRIES)
 		return false;
 
 	/*
@@ -3425,7 +3435,7 @@ should_reclaim_retry(gfp_t gfp_mask, unsigned order,
 		unsigned long reclaimable;
 
 		available = reclaimable = zone_reclaimable_pages(zone);
-		available -= DIV_ROUND_UP(no_progress_loops * available,
+		available -= DIV_ROUND_UP((*no_progress_loops) * available,
 					  MAX_RECLAIM_RETRIES);
 		available += zone_page_state_snapshot(zone, NR_FREE_PAGES);
 
@@ -3641,18 +3651,8 @@ __alloc_pages_slowpath(gfp_t gfp_mask, unsigned int order,
 	if (order > PAGE_ALLOC_COSTLY_ORDER && !(gfp_mask & __GFP_REPEAT))
 		goto nopage;
 
-	/*
-	 * Costly allocations might have made a progress but this doesn't mean
-	 * their order will become available due to high fragmentation so
-	 * always increment the no progress counter for them
-	 */
-	if (did_some_progress && order <= PAGE_ALLOC_COSTLY_ORDER)
-		no_progress_loops = 0;
-	else
-		no_progress_loops++;
-
 	if (should_reclaim_retry(gfp_mask, order, ac, alloc_flags,
-				 did_some_progress > 0, no_progress_loops))
+				 did_some_progress > 0, &no_progress_loops))
 		goto retry;
 
 	/*
-- 
2.10.0