Messages in this thread | | | Date | Wed, 06 Mar 2013 02:14:11 -0800 | From | Howard Chu <> | Subject | Re: mmap vs fs cache |
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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. 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. http://www.symas.com Director, Highland Sun http://highlandsun.com/hyc/ Chief Architect, OpenLDAP http://www.openldap.org/project/
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