Re: [PATCH v2 4/4] mm: add WasActive page flag

[Bob Liu <bob.liu@oracle.com>]

Hi Pekka,

On 08/13/2013 02:01 PM, Pekka Enberg wrote:
> On 8/6/13 2:36 PM, Bob Liu wrote:
>> Zcache could be ineffective if the compressed memory pool is full with
>> compressed inactive file pages and most of them will be never used again.
>>
>> So we pick up pages from active file list only, those pages would
>> probably be
>> accessed again. Compress them in memory can reduce the latency
>> significantly
>> compared with rereading from disk.
>>
>> When a file page is shrinked from active file list to inactive file list,
>> PageActive flag is also cleared.
>> So adding an extra WasActive page flag for zcache to know whether the
>> file page
>> was shrinked from the active list.
>>
>> Signed-off-by: Bob Liu <bob.liu@oracle.com>
> 

Thank you so much for your review!

> Using a page flag for this seems like an ugly hack to me.
> Can we rearrange the code so that vmscan notifies zcache
> *before* the active page flag is cleared...?

Yep, adding a page flag is not a good idea.
I'm looking at whether there is other way to notify zcache.

BTW: Could you please give some feedback too about other zcache patches?

> 
>                 Pekka

-- 
Regards,
-Bob

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