Re: [RFC][PATCH] ring-buffer: Replace this_cpu_{read,write} with this_cpu_ptr()

From: Christoph Lameter
Date: Tue Mar 17 2015 - 01:56:58 EST

On Mon, 16 Mar 2015, Steven Rostedt wrote:

> It has come to my attention that this_cpu_read/write are horrible on
> architectures other than x86. Worse yet, they actually disable
> preemption or interrupts! This caused some unexpected tracing results
> on ARM.

Well its just been 7 years or so. Took a long time it seems.

These would need to be implemented on the architectures to
have comparable performance.

> I may go and remove all this_cpu_read,write() calls from my code
> because of this.

You could do that with __this_cpo_* but not this_cpu_*(). Doing
it to this_cpu_* would make the operations no longer per cpu atomic. If
they do not need per cpu atomicity then you could have used __this_cpu_*
instead. And __this_cpu_* do not disable preemption or interrupts.

So please do not send patches based on gut reactions.


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