Messages in this thread | | | Date | Thu, 13 Apr 2017 20:29:39 +0200 | From | Peter Zijlstra <> | Subject | Re: [PATCH tip/core/rcu 04/13] rcu: Make RCU_FANOUT_LEAF help text more explicit about skew_tick |
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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.
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