Re: [bisected] pre-3.16 regression on open() scalability

From: Paul E. McKenney
Date: Thu Jun 19 2014 - 16:44:57 EST


On Thu, Jun 19, 2014 at 03:31:56PM -0500, Christoph Lameter wrote:
> On Thu, 19 Jun 2014, Paul E. McKenney wrote:
>
> > That is a separate issue, but unnecessary calls to cond_resched()
> > should of course be removed -- no argument there.
>
> It looks like we are fighting higher latencies by adding calls in most of
> the critical sections which will in turn increase the latencies that we
> are trying to reduce.

That is on battle in a larger war. Another battle is to keep big systems
from choking and dying. We need to win both battles, though I understand
that you are focused primarily on latency reduction. I don't get that
luxury because RCU is used across the board.

Thanx, Paul

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