Re: [PATCH tip/core/rcu] Reduce overhead of cond_resched() checks for RCU

From: Christoph Lameter
Date: Mon Jun 23 2014 - 09:53:20 EST


On Fri, 20 Jun 2014, Paul E. McKenney wrote:

> > I like this approach *far* better. This is the kind of thing I had in
> > mind when I suggested using the fqs machinery: remove the poll entirely
> > and just thwack a CPU if it takes too long without a quiescent state.
> > Reviewed-by: Josh Triplett <josh@xxxxxxxxxxxxxxxx>
>
> Glad you like it. Not a fan of the IPI myself, but then again if you
> are spending that must time looping in the kernel, an extra IPI is the
> least of your problems.

Good. The IPI is only used when actually necessary. The code inserted
was always there and always executed although rarely needed.

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