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

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Date:   Fri, 23 Sep 2016 08:55:33 +0200
From:   Vlastimil Babka <vbabka@...e.cz>
To:     Hillf Danton <hillf.zj@...baba-inc.com>,
        '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 09/23/2016 06:04 AM, Hillf Danton wrote:
>>
>> ----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;
> 
> s/no/*no/
>> +	else
>> +		no_progress_loops++;
> 
> s/no_progress_loops/(*no_progress_loops)/

Crap, thanks. I'm asking our gcc guy about possible warnings for this,
and some past mistake I've seen which would be *no_progress_loops++.
 
> With that feel free to add
> Acked-by: Hillf Danton <hillf.zj@...baba-inc.com>

Thanks!

----8<----
>From 1623d5bd441160569ffad3808aeeec852048e558 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.

[hillf.zj@...baba-inc.com: fix missing pointer dereferences]
Signed-off-by: Vlastimil Babka <vbabka@...e.cz>
Acked-by: Hillf Danton <hillf.zj@...baba-inc.com>
---
 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..6039ff40452c 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