Re: [PATCH tip/core/rcu] Reduce overhead of cond_resched() checks for RCU

From: Paul E. McKenney
Date: Mon Jun 23 2014 - 12:45:43 EST


On Mon, Jun 23, 2014 at 08:51:08AM -0500, Christoph Lameter wrote:
> On Mon, 23 Jun 2014, Peter Zijlstra wrote:
>
> > On the topic of these threads; I recently noticed RCU grew a metric ton
> > of them, I found some 75 rcu kthreads on my box, wth up with that?
>
> Would kworker threads work for rcu? That would also avoid the shifting
> around of RCU threads for NOHZ configurations (which seems to have to be
> done manually right now). The kworker subsystem work that allows
> restriction to non NOHZ hardware threads would then also allow the
> shifting of the rcu threads which would simplify the whole endeavor.

Short term, I am planning to use a different method to automate the
binding of the rcuo kthreads to housekeeping CPUs, but longer term,
it might well make a lot of sense to move to workqueues and the kworker
threads.

Thanx, Paul

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