Re: [RFC/PATCH 2/5] kernel_cpustat: convert to atomic 64-bitaccessors

From: Russell King - ARM Linux
Date: Thu Feb 21 2013 - 16:59:16 EST

On Thu, Feb 21, 2013 at 10:53:07PM +0100, Frederic Weisbecker wrote:
> That too should be kcpustat_this_cpu_set(), or kcpustat_this_cpu_add()
> FWIW. But we probably don't need the overhead of atomic_add() that
> does a LOCK.
> atomic_set(var, atomic_read(var) + delta) would be better. All we need

You mean atomic64_set() and atomic64_read(). Looking at the generic
version in lib/atomic64.c, atomic64_add() is cheaper for 32-bit arches
because it doesn't involve taking the lock twice.
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