Messages in this thread | | | Date | Mon, 23 Sep 2013 10:04:00 -0700 | From | "Paul E. McKenney" <> | Subject | Re: [PATCH] hotplug: Optimize {get,put}_online_cpus() |
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On Mon, Sep 23, 2013 at 06:01:30PM +0200, Peter Zijlstra wrote: > On Mon, Sep 23, 2013 at 08:50:59AM -0700, Paul E. McKenney wrote: > > Not a problem, just stuff the idx into some per-task thing. Either > > task_struct or taskinfo will work fine. > > Still not seeing the point of using srcu though.. > > srcu_read_lock() vs synchronize_srcu() is the same but far more > expensive than preempt_disable() vs synchronize_sched().
Heh! You want the old-style SRCU. ;-)
> > Or to put it another way, if the underlying slow-path mutex is > > reader-preference, then the whole thing will be reader-preference. > > Right, so 1) we have no such mutex so we're going to have to open-code > that anyway, and 2) like I just explained in the other email, I want the > pending writer case to be _fast_ as well.
At some point I suspect that we will want some form of fairness, but in the meantime, good point.
Thanx, Paul
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