On Tue, Oct 25, 2011 at 11:24 PM, David Rientjes <rientjes@xxxxxxxxxx> wrote:
> On Tue, 25 Oct 2011, Colin Cross wrote:
>
>> > Or, rather, when pm_restrict_gfp_mask() clears __GFP_IO and __GFP_FS that
>> > it also has the same behavior as __GFP_NORETRY in should_alloc_retry() by
>> > setting a variable in file scope.
>> >
>>
>> Why do you prefer that over adding a gfp_required_mask?
>>
>
> Because it avoids an unnecessary OR in the page and slab allocator
> fastpaths which are red hot :)
>
Makes sense. What about this? Official patch to follow.
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index fef8dc3..59cd4ff 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -1786,6 +1786,13 @@ should_alloc_retry(gfp_t gfp_mask, unsigned int order,
return 0;
/*
+ * If PM has disabled I/O, OOM is disabled and reclaim is unlikely
+ * to make any progress. To prevent a livelock, don't retry.
+ */
+ if (!(gfp_allowed_mask & __GFP_FS))
+ return 0;
+
+ /*
* In this implementation, order <= PAGE_ALLOC_COSTLY_ORDER
* means __GFP_NOFAIL, but that may not be true in other
* implementations.
--
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