lkml.org 
[lkml]   [2015]   [Jun]   [24]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [RFC][PATCH 12/13] stop_machine: Remove lglock
On Wed, Jun 24, 2015 at 07:50:42AM -0700, Paul E. McKenney wrote:
> On Wed, Jun 24, 2015 at 09:35:03AM +0200, Peter Zijlstra wrote:

> > I still don't see a problem here though; the stop_one_cpu() invocation
> > for the CPU that's suffering its preemption latency will take longer,
> > but so what?
> >
> > How does polling and dropping back to sync_rcu() generate better
> > behaviour than simply waiting for the completion?
>
> Because if there is too much delay, synchronize_rcu() is no slower
> than is synchronize_rcu_expedited(), plus synchronize_rcu() is much
> more efficient.

Still confused.. How is polling and then blocking more efficient than
just blocking in the first place? I'm seeing the polling as a waste of
cpu time.

The thing is, if we're stalled on a stop_one_cpu() call, the sync_rcu()
is equally stalled. The sync_rcu() cannot wait more efficient than we're
already waiting either.




\
 
 \ /
  Last update: 2015-06-24 17:21    [W:0.333 / U:0.308 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site