Re: [RFC PATCH] do_try_to_free_pages() might enter infinite loop

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On Tue, Apr 24, 2012 at 9:38 AM, Rik van Riel <riel@xxxxxxxxxx> wrote:
> On 04/24/2012 12:36 PM, Ying Han wrote:
>
>> However, what if B frees a pages everytime before pages_scanned
>> reaches the point, then we won't set zone->all_unreclaimable at all.
>> If so, we reaches a livelock here...
>
>
> If B keeps freeing pages, surely A will get a successful
> allocation and there will not be a livelock?

Ah, that is another piece of puzzle. We suspect the zone is under
min_watermark due to previous alloc_flags (ALLOC_NO_WATERMARKS) and B
returns the page under min which can not be allocated by A.

Now we reset the zone->pages_scanned on freeing page regardless of the
watermarks, so it is possible that zone is under min_watermark but
!zone->all_unreclaimable.

--Ying

>
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