Re: [PATCH 2/3][v2] vmstat: add anon_scan_ratio field to zoneinfo

From: Minchan Kim
Date: Sun Jan 17 2010 - 21:25:27 EST

On Mon, Jan 18, 2010 at 11:16 AM, Rik van Riel <riel@xxxxxxxxxx> wrote:
> On 01/17/2010 09:10 PM, Minchan Kim wrote:
>> Absoultely right. I missed that. Thanks.
>> get_scan_ratio used lru_lock to get reclaim_stat->recent_xxxx.
>> But, it doesn't used lru_lock to get ap/fp.
>> Is it intentional? I think you or Rik know it. :)
>> I think if we want to get exact value, we have to use lru_lock until
>> getting ap/fp.
>> If it isn't, we don't need lru_lock when we get the
>> reclaim_stat->recent_xxxx.
>> What do you think about it?
> This is definately not intentional.
> Getting race conditions in this code could throw off the
> statistics by a factor 2. ÂI do not know how serious that
> would be for the VM or whether (and how quickly) it would
> self correct.

Okay. How about making patch to get exact ap/fp?
Although it were not serious or fast recoverable, I think it would be better
to protect lru_lock for consistency if lru_lock isn't big contention lock.

> --
> All rights reversed.

Kind regards,
Minchan Kim
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