Chris,
I think that "reclaiming pages from the page cache" is the PROBLEM,
not the solution. If I understand you correctly a lower value of
"swappiness" means that the ANONYMOUS pages of an application's stack
and heap are less likely to be subject to swap I/O. However, the
concern here is for the pages of an mmap()ed file (though an unlinked
one). So, my expectation is that the page cache is their "owner" rather
than the application. If that is an incorrect understanding, I would
appreciate being corrected.
-Paul
Christopher Samuel wrote:
-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1
On 10/06/10 18:43, Paul H. Hargrove wrote:
> When the file is on a real (not tmpfs or other ramdisk) I am 95% certain
> that this is an artifact of the Linux swapper/pager behavior which is
> thinking it is being smart by "swapping ahead". Even when there is no
> memory pressure that requires swapping, Linux starts queuing swap I/O
> for pages to keep the number of "clean" pages up when possible.
I believe you can tweak that behaviour through the VM subsystem
using /proc/sys/vm/swappiness, it defaults to 60 but lower values
are meant to make the kernel less likely to swap out applications
and instead concentrate on reclaiming pages from the page cache.
cheers,
Chris
- --
Christopher Samuel - Senior Systems Administrator
VLSCI - Victorian Life Sciences Computational Initiative
Email: sam...@unimelb.edu.au Phone: +61 (0)3 903 55545
http://www.vlsci.unimelb.edu.au/
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.4.10 (GNU/Linux)
Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org/
iEYEARECAAYFAkwR0fcACgkQO2KABBYQAh8sEACggnFKMQIVummW21teI9yBqqNt
T4AAnjMSfOFONLyANjgso7kO0VAH3zi7
=X3AE
-----END PGP SIGNATURE-----
------------------------------------------------------------------------
_______________________________________________
devel mailing list
de...@open-mpi.org
http://www.open-mpi.org/mailman/listinfo.cgi/devel
--
Paul H. Hargrove phhargr...@lbl.gov
Future Technologies Group
HPC Research Department Tel: +1-510-495-2352
Lawrence Berkeley National Laboratory Fax: +1-510-486-6900
