On Jan 23, 2007  10:39 -0800, Sridharan Ramaswamy (srramasw) wrote:
> I'm tring to measure the overhead of having Lustre on the system.  Among
> other things, I noticed it starts lot of processes,
>  
> root      4565     1  0 Jan03 ?        00:00:00 [ll_mdt_attr_14]
> root      4636     1  0 Jan03 ?        00:00:01 [ll_ost_13]
> root      4651     1  0 Jan03 ?        00:00:08 [ll_ost_io_13]
> root      4550     1  0 Jan03 ?        00:00:03 [ll_mdt_14]
> root      4516     1  0 Jan03 ?        00:00:00 [ldlm_cb_31]
> 
> I can account about 200 processes related to Lustre on an OST node. That
> seems a lot considering we would like to run other applications on the
> same node. Is it possible to tune these number of processes down? Say
> reduce 32 ldlm process to about 8. What kind of performance degradation
> to expect if we can do that?

You can reduce the MDS and OST process count via modprobe.conf:

option mds mds_num_threads=NNN
option ost ost_num_threads=NNN

If this isn't good enough, you can change the count at compile time
in lustre/include/linux/lustre-net.h

In 1.6 the number of threads will be more dynamic, depending on load.

Cheers, Andreas
--
Andreas Dilger
Principal Software Engineer
Cluster File Systems, Inc.

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