[OpenAFS] clarification on client caches

Derrick J Brashear shadow@dementia.org
Mon, 6 Sep 2004 18:34:15 -0400 (EDT)

On Mon, 6 Sep 2004, Wes Chow wrote:

> Case 1: If I start with the cache size I want and "-chunksize 20" as
> the only afsd option, after afsd finishes creation of the cache,
> afs_cachetrim then proceeds to use up most of the CPU in what appears
> to be an infinite loop.  I've let it run for about 4 hours and it
> never stopped.  Accesses to /afs work, but the computer is
> understandably slow.

Perhaps some hash table is overflowing in a bad way? I'd expect if you 
make the chunksize ever larger (and the number of files will get fewer on 
their own) that is this is the problem, it will go away.

> Case 2: What I'm doing now is limiting the number of V files by using
> the "-files 50000" option.  If I start it out at the cache size I want
> (30 gigs), accesses to /afs hang without afs_cachetrim running amok.

fstrace might give you hints. fstrace setset cm -active
then, fstrace dump cm
when it starts hanging

if you get "raw op" stuff, you failed to install the afszcm.cat file.

> However, if I lower the cache size it seems to work.  Starting at a
> lower cache size and resizing upwards doesn't seem to help.

i wouldn't expect it to.

> Is it not typical to have cache sizes of this size?

sadly no. most of my test hosts don't have that much free disk, and a few 
don't have that much disk period.