Re: mmap vs fs cache

[Howard Chu <hyc@symas.com>]

Howard Chu wrote:
> Howard Chu wrote:
>> Howard Chu wrote:
>>> 2 questions:
>>>       why is there data in the FS cache that isn't owned by (the mmap of) the
>>> process that caused it to be paged in in the first place?
>>>       is there a tunable knob to discourage the page cache from stealing from the
>>> process?
>>
>> This Unmapped page cache control http://lwn.net/Articles/436010/ sounds like
>> it might have been helpful here. I.e., having a way to prioritize so that
>> unmapped cache pages get reclaimed in preference to mapped pages could help.
>> Though I still don't understand why these pages in the cache aren't mapped in
>> the first place.
>>
> As implied by this post
> http://lkml.indiana.edu/hypermail/linux/kernel/0701.3/0354.html setting
> swappiness to 0 seems to give the desired effect of preventing mapped pages
> from being reclaimed.

I spoke too soon, after a few minutes of load the process size started 
shrinking again. My original questions still stand.

-- 
   -- Howard Chu
   CTO, Symas Corp.           http://www.symas.com
   Director, Highland Sun     http://highlandsun.com/hyc/
   Chief Architect, OpenLDAP  http://www.openldap.org/project/