Re: mmap vs fs cache

Howard Chu
2013-03-06T10:22:53Z

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/