Messages in this thread | | | Date | Wed, 7 Feb 2018 20:10:39 -0800 | From | "Paul E. McKenney" <> | Subject | Re: [PATCH 0/2] rcu: Transform kfree_rcu() into kvfree_rcu() |
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On Wed, Feb 07, 2018 at 01:26:19PM -0500, Steven Rostedt wrote: > On Wed, 7 Feb 2018 10:10:55 -0800 > Matthew Wilcox <willy@infradead.org> wrote: > > > > For the record, I fully agree with Steve here. > > Thanks, but... > > > > > > > And being a performance "fanatic" I don't like to have the extra branch > > > (and compares) in the free code path... but it's a MM-decision (and > > > sometimes you should not listen to "fanatics" ;-)) > > > > While free_rcu() is not withut its performance requirements, I think it's > > currently dominated by cache misses and not by branches. By the time RCU > > gets to run callbacks, memory is certainly L1/L2 cache-cold and probably > > L3 cache-cold. Also calling the callback functions is utterly impossible > > for the branch predictor. > > I agree with Matthew. > > This is far from any fast path. A few extra branches isn't going to > hurt anything here as it's mostly just garbage collection. With or > without the Spectre fixes.
What Steve said!
Thanx, Paul
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