[OpenAFS] Apache and Openafs

GALAMBOS Daniel dancsa@dancsa.hu
Thu, 26 Dec 2013 15:48:41 +0100


Our webservice built onto AFS, one node provide the static data, and
works as a proxy for PHP.
On this server, we have performance problem with AFS. This is a Debian
Wheezy with afs client 1.6.1-3+deb7u1.

So we got problems, i cloned the machine and started testing. I used
apache benchmark (ab) against a simple html (w/o pictures or anything,
just text). If i downloaded it 2000 times with 50 thread i got high load
(18) and ~20 000 context switching in vmstat. The same file with 100
thread generated ~50 load.

afsd is started with the following options:
OPTIONS="-stat 10000 -dcache 10000 -daemons 6 -volumes 2048 -memcache
-chunksize 18 -rxpck 750 -rxmaxmtu 1500 -prealloc 750"

cache size is: 3065648

During the tests no other connection ( except apache status query 1/sec)
was made, the same file was asked for 2000 times.

After reading old messages on this list, i decreased the daemons to 3,
which caused a very little improvement.  Reading the apache status i
noticed, that the apache spends 4-5 times more time in kernel space than
in users pace.  When the same file hosted on the local filesystem the
avg response time decreased from 1800 ms to 50 ms and there are almost
no load.

Could you help me with this?