Cachefiles question

Cachefiles question

[Lukas Hejtmanek]

Hello,

what is fscache newly added into mainline supposed to do?

I thought it is used as writeback cache and read cache for network file
systems. But it appears that it does not do any writeback and it seems it
caches only few reads.

I put whole Linux kernel sources on my NFS volume, mounted with fcs option,
have cachefilesd running. I did: make defconfig, make -j4. I put my caching
files into /opt/fscache:
cat /etc/cachefilesd.conf 
dir /opt/fscache


however, after the build is complete:
/opt/fscache# du -sm
2	.

so it looks like only 2MB of total 572MB is cached. I'm I something missing or the
fscache should not be better than this?

/opt is 491GB and uses XFS.

even after taring whole kernel sources, fscache does not consume more free
space.

-- 
Lukáš Hejtmánek

Re: Cachefiles question

[David Howells]

Lukas Hejtmanek <xhejtman@ics.muni.cz> wrote:

> what is fscache newly added into mainline supposed to do?
> 
> I thought it is used as writeback cache and read cache for network file
> systems. But it appears that it does not do any writeback and it seems it
> caches only few reads.

It only caches files on NFS that are opened for reading at the moment due to
coherency issues.

> however, after the build is complete:
> /opt/fscache# du -sm
> 2	.

Is there anything in dmesg?

And can you check /proc/fs/fscache/stats?

David