On 09/21/2016 07:13 PM, Michal Hocko wrote:
> On Tue 06-09-16 15:52:56, Vlastimil Babka wrote:
> [...]
>> @@ -3204,6 +3199,15 @@ should_compact_retry(struct alloc_context *ac, int 
>> order, int alloc_flags,
>>      if (compaction_retries <= max_retries)
>>              return true;
>>  
>> +    /*
>> +     * Make sure there is at least one attempt at the highest priority
>> +     * if we exhausted all retries at the lower priorities
>> +     */
>> +check_priority:
>> +    if (*compact_priority > MIN_COMPACT_PRIORITY) {
>> +            (*compact_priority)--;
>> +            return true;
> 
> Don't we want to reset compaction_retries here? Otherwise we can consume
> all retries on the lower priorities.

Good point, patch-fix below.

> Other than that it looks good to me. With that you can add
> Acked-by: Michal Hocko <mho...@suse.com>

Thanks!
 
>> +    }
>>      return false;
>>  }
>>  #else
> 

----8<----
>From 465e1bd61b7a6d6901a44f09b1a76514dbc220fa Mon Sep 17 00:00:00 2001
From: Vlastimil Babka <vba...@suse.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.

Suggested-by: Michal Hocko <mho...@suse.com>
Signed-off-by: Vlastimil Babka <vba...@suse.cz>
---
 mm/page_alloc.c | 13 +++++++------
 1 file changed, 7 insertions(+), 6 deletions(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index f8bed910e3cf..82fdb690ac62 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -3162,7 +3162,7 @@ static inline bool
 should_compact_retry(struct alloc_context *ac, int order, int alloc_flags,
                     enum compact_result compact_result,
                     enum compact_priority *compact_priority,
-                    int compaction_retries)
+                    int *compaction_retries)
 {
        int max_retries = MAX_COMPACT_RETRIES;
 
@@ -3196,16 +3196,17 @@ should_compact_retry(struct alloc_context *ac, int 
order, int alloc_flags,
         */
        if (order > PAGE_ALLOC_COSTLY_ORDER)
                max_retries /= 4;
-       if (compaction_retries <= max_retries)
+       if (*compaction_retries <= max_retries)
                return true;
 
        /*
-        * Make sure there is at least one attempt at the highest priority
-        * if we exhausted all retries at the lower priorities
+        * Make sure there are attempts at the highest priority if we exhausted
+        * all retries or failed at the lower priorities.
         */
 check_priority:
        if (*compact_priority > MIN_COMPACT_PRIORITY) {
                (*compact_priority)--;
+               *compaction_retries = 0;
                return true;
        }
        return false;
@@ -3224,7 +3225,7 @@ static inline bool
 should_compact_retry(struct alloc_context *ac, unsigned int order, int 
alloc_flags,
                     enum compact_result compact_result,
                     enum compact_priority *compact_priority,
-                    int compaction_retries)
+                    int *compaction_retries)
 {
        struct zone *zone;
        struct zoneref *z;
@@ -3663,7 +3664,7 @@ __alloc_pages_slowpath(gfp_t gfp_mask, unsigned int order,
        if (did_some_progress > 0 &&
                        should_compact_retry(ac, order, alloc_flags,
                                compact_result, &compact_priority,
-                               compaction_retries))
+                               &compaction_retries))
                goto retry;
 
        /* Reclaim has failed us, start killing things */
-- 
2.10.0


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