[Gluster-devel] High CPU usage -- any way to reduce cpu load?

[billy cokalopolous]

I'm currently testing a 1 node architecture as I was having problems with
afr and multinode performance.

write and read performance to glusterfs (single node) is now good, but when
running mysql on top of glusterfs, performance drops dramatically due to
high cpu usage.

mysql is mounted to the glusterfs & glusterfsd is running on the same node.

When running a simple query accessing one table, the cpu load from glusterfs
/ glusterfsd in top are relatively low.

When running a 3 table join (18 files must be read, myi,myd,frm for each
table, 2 tables per virtual table, so 3*3*2), the glusterfs/glusterfsd cpu
load skyrockets stealing the cpu away from mysql processing.

So this query on the local fs (ext3) takes 4 seconds, while the single node
glusterfs takes 22 seconds.

I've adjusted iothreads, iocache, readahead, etc,etc. None of these options
make a difference in the cpu load. Tried using posix-locks and then posix.

I wonder if glusterfs and mysql are stepping on each other's toes to cause
this high load? Might the issue lie in tuning the file system & kernel
params? Or is this cpu usage expected load?

Thanks.