cache quota

cache quota

[sanoj]

Hello
my doubt is if linux has any user quota for the usage of page cache,
i.e. if a user is doing a disk intensive operation, will the I/O performance
for other users other users be affected as they
may incur more cache misses.

thanks,
sanoj
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cache quota

[Rajat Sharma]

Hi Sanoj,

Linux page cache is a shared resource which any process accessing the file
can access. There is no mechanism within generic page cache handler to
support such quota mechanism, as there is no meta information attached with
the page in pagecache.

However it looks possible to me to implement it within a file-system by
defining a wrapper structure above each page in page-cache which can hold
per user information about the page. NFS maintains a wrapper structure
nfs_page over dirty page-cache pages and maintains credentials of user
within this structure. However purpose of doing so is for correctness and
flush any incompatible pages to NFS server before writing new dirty page to
page cache.

It feasible to implement such quota schemes, but may come up with some
performance implications and maintenance cost will be high for such a code.
But anyways, if you plan to implement such a file-system (or modify existing
one), it can be a nice learning project. Infact many people keep looking for
kernel project on this list, this looks to me a great idea for that matter.

Rajat

On Thu, Jan 6, 2011 at 3:25 PM, sanoj <k.u.sanoj@gmail.com> wrote:
> Hello
> my doubt is if linux has any user quota for the usage of page cache,
> i.e. if a user is doing a disk intensive operation, will the I/O
performance
> for other users other users be affected as they
> may incur more cache misses.
> thanks,
> sanoj
>
> _______________________________________________
> Kernelnewbies mailing list
> Kernelnewbies at kernelnewbies.org
> http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
>
>
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