On Thu, Dec 16, 2004 at 04:17:53PM -0600, John Goerzen wrote:
<snip> 
> I noticed my problems during runs of updatedb (for locate).  That
> process basically reads a bunch of directories, probably stats all the
> files, but never actually opens the files.  (I think it runs find.)
 
> I wonder if this has something to do with directories or inodes.
> 
> I haven't lately noticed it with updatedb runs, but I have noticed it
> periodically when copying, or building ISO images or things like that.

Yes, again this sounds similar to a problem someone reported a week or
two ago, where he had a directory with 500k files and was running find
on it.  The symptoms will be that kswapd is running a lot and system
responsiveness will be very poor.  Also, it's certainly possible that
some of your directorys will have very few files, but what's important
is the total number of inodes in memory, not any particular directory.

You should look at the number of inodes incore at this point, and this
will give you an idea of whether this is the problem or not.  Do this
by using either "slabtop" or looking at /proc/slabinfo and looking at
the number of slabs used for dentrys and inodes.

If this is indeed the problem, one stopgap measuere on > 2.6.7 kernels
is to alter the value of /proc/sys/vm/vfs_cache_pressre upwards.  I
would try values with different orders of magnitude, i.e. 1000, 10000,
100000, etc.  This should cause kswapd to be more aggressive in
eliminating slab objects, which means it will hold the dcache for less
time overall.

Sonny
 
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