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SubjectRe: mmap vs fs cache
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 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 setting
swappiness to 0 seems to give the desired effect of preventing mapped pages
from being reclaimed. If this is an intended effect, it would be nice to have
this documented in Documentation/sysctl/vm.txt. If this is not the intended
effect, please don't "fix" this without providing a supported means of doing
the same.

-- Howard Chu
CTO, Symas Corp.
Director, Highland Sun
Chief Architect, OpenLDAP

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