Re: mmap vs fs cache

[Howard Chu]

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/
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/