[Lustre-discuss] oss_num_threads & oss_num_create_threads

[Johann Lombardi]

On Thu, Mar 11, 2010 at 10:43:28AM -0600, Hendelman, Rob wrote:
> I'd like to make sure that I understand these 2 module options.
> 
> >From googling a bit & searching bugzilla, here is my understanding:
> 
> oss_num_threads = Maximum number of service threads across all ost's on a single OSS.
> oss_num_create_threads = minimum number of threads across all ost's on a single oss (Number of threads when module is loaded even if no i/o)
> 
> Is this correct or am I misunderstanding?

Not exactly. First of all, oss_num_threads and oss_num_create_threads apply
to different set of service threads. oss_num_create_threads is for the
ll_ost_create threads which are in charge of statfs and object creation
requests, while oss_num_threads is for the ll_ost and ll_ost_io threads
which handle all the other requests (read/write, truncate, setattr, ...).

By default, we start a mininum number of threads for each service and fork
new service threads on demand based on load, up to a max value.
Setting oss_num_threads/oss_num_create_threads disables dynamic thread
creation and just starts the number of threads you've asked for.

Cheers,
Johann