lkml.org 
[lkml]   [2017]   [Apr]   [13]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH tip/core/rcu 04/13] rcu: Make RCU_FANOUT_LEAF help text more explicit about skew_tick
On Thu, Apr 13, 2017 at 10:31:00AM -0700, Paul E. McKenney wrote:
> On Thu, Apr 13, 2017 at 07:04:34PM +0200, Peter Zijlstra wrote:

> > And I have vague memories of it actually causing lock contention, but
> > I've forgotten how that worked.
>
> That is a new one on me. I can easily see how not skewing ticks could
> cause serious lock contention, but am missing how skewed ticks would
> do so.

It could've been something like cacheline bouncing. Where with a
synchronized tick, the (global) cacheline would get used by all CPUs on
a node before heading out to the next node etc.. Where with a skewed
tick, it would forever bounce around.

\
 
 \ /
  Last update: 2017-04-13 20:30    [W:0.073 / U:0.564 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site