Re: [PATCH] sched/rt: don't try to balance rt_runtime when it is futile

[Paul E. McKenney]

On Thu, May 15, 2014 at 05:18:51AM +0200, Mike Galbraith wrote:
> On Wed, 2014-05-14 at 08:44 -0700, Paul E. McKenney wrote:
> 
> > In practice, not sure how much testing CONFIG_NO_HZ_FULL=y has received
> > for -rt kernels in production environments.
> 
> I took 3.14-rt out for a quick spin on my 64 core box, it didn't work at
> all with 60 cores isolated.  I didn't have time to rummage, but it looks
> like there are still bugs to squash. 
> 
> Biggest problem with CONFIG_NO_HZ_FULL is the price tag.  It just raped
> fast mover performance last time I measured.

I do have a report of the RCU grace-period kthreads (rcu_preempt,
rcu_sched, and rcu_bh) consuming excessive CPU time on large boxes,
but this is for workloads with lots of threads and context switches.

Whether relevant or not to your situation, working on it...

							Thanx, Paul

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/