[Gluster-devel] Quick Question: glusterFS and kernel (stat) caching
avati at zresearch.com
Wed Aug 8 08:31:41 UTC 2007
Can you checkout the latest repository snapshot and re-run your tests,
except this time mounting glusterfs with '--entry-timeout 10.0--attr-timeout
10.0' which sets and entry and attribute timeouts of 10 seconds for every
2007/8/8, Anand Avati <avati at zresearch.com>:
> In fuse based filesystems, the filesystem can set the stat cache timeout
> value. By default it is 1 second. On disk based filesystems this timeout is
> 'infinite' (till the dentry cache is shrunk, stat() never goes to the disk
> for a second time). But for network based filesystems it is unsafe to set
> such high stat cache timeouts. Still you are free to try. Currently in the
> GlusterFS codebase this value is hardcoded to 1 sec. I'll be adding a
> command line argument to set this timeout for you to experiment with it.
> Please let us know your results.
> 2007/8/6, Bernhard J. M. Grün <bernhard.gruen at googlemail.com>:
> > Hello developers!
> > At the moment we try to optimize our web server setup again.
> > We tried to parallelize the stat calls in our web server software
> > (lighttpd). But it seems the kernel does not cache the stat
> > information from one request for further requests. But the same setup
> > works fine on a local file system. So it seems that glusterFS and/or
> > FUSE is not able to communicate with the kernel (stat) cache. Is this
> > right? And is this problem solvable?
> > Here is some schematic diagram of our approach:
> > request -> lighttpd -> Threaded FastCGI program, that does only a stat
> > (via fopen) -> lighttpd opens the file for reading and writes the date
> > to the socket
> > In a local scenario the second open uses the cached stat and so it
> > does not block other reads in lighty at that point. but with a
> > glusterFS mount it still blocks there.
> > Maybe you can give me some advice. Thank you!
> > Bernhard J. M. Grün
> > _______________________________________________
> > Gluster-devel mailing list
> > Gluster-devel at nongnu.org
> > http://lists.nongnu.org/mailman/listinfo/gluster-devel
> It always takes longer than you expect, even when you take into account
> Hofstadter's Law.
> -- Hofstadter's Law
It always takes longer than you expect, even when you take into account
-- Hofstadter's Law
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