Re: [PATCH 0/2] cpustat: use atomic operations to read/update stats
From: Eric Dumazet
Date: Fri Feb 22 2013 - 09:21:42 EST
On Fri, 2013-02-22 at 15:09 +0100, Peter Zijlstra wrote:
> 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.
We also have include/linux/u64_stats_sync.h since 2.6.36
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