Re: [PATCH 0/2] cpustat: use atomic operations to read/update stats

From: Peter Zijlstra
Date: Fri Feb 22 2013 - 09:09:31 EST

On Fri, 2013-02-22 at 13:50 +0100, Frederic Weisbecker wrote:
> > Argh!! at what cost? 64bit atomics are like expensive. Wouldn't
> adding
> > a seqlock be saner?
> Not sure. This requires a spinlock in the write side which is called
> from
> fast path like the timer interrupt.

A single spinlock is _way_ cheaper than a ton of cmpxchg8b()s to update
a few variables.

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