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

[Frederic Weisbecker]

2013/2/21 Russell King - ARM Linux <linux@xxxxxxxxxxxxxxxx>:
> 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().

Right.

> 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.

Yeah but that's the generic version. I guess the archs that have
overriden don't take any locks there.
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