[sheepdog] [PATCH v2 5/5] work: shrink the number of worker threads dynamically

[MORITA Kazutaka]

At Thu, 28 Feb 2013 20:17:23 +0800,
Liu Yuan wrote:
> 
> On 02/28/2013 08:09 PM, MORITA Kazutaka wrote:
> > At Thu, 28 Feb 2013 19:28:32 +0800,
> > Liu Yuan wrote:
> >>
> >> On 02/28/2013 06:46 PM, MORITA Kazutaka wrote:
> >>> +	if (wi->nr_pending + wi->nr_running <= wi->nr_threads / 2)
> >>> +		/* we cannot shrink work queue during protection period. */
> >>> +		return wi->tm_end_of_protection <= get_msec_time();
> >>
> >> Why we need delay shrinking?
> > 
> > To avoid many calls of pthread_create.  Without it, threads are
> > frequently created and deleted like short threads, and it leads poor
> > performance on my environment.
> > 
> 
> Then we'd better embed this as comment.

Okay.

> And what about longer delay,
> which might further reduce the false shrinking?

It's a trade-off with an efficient use of resources.  If we use a
longer value, we may keep too many threads.

There is no rationale for 1 second for now.  I think we should change
it after we merge this series and see how it works on actual
environment.

Thanks,

Kazutaka