Re: [PATCH v2 1/2] mm/slub: optimize alloc/free fastpath by removing preemption on/off

[Christoph Lameter]

On Thu, 15 Jan 2015, Steven Rostedt wrote:

> profiling function tracing I discovered that accessing preempt_count
> was actually quite expensive, even just to read. But it may not be as
> bad since Peter Zijlstra converted preempt_count to a per_cpu variable.
> Although, IIRC, the perf profiling showed the access to the %gs
> register was where the time consuming was happening, which is what
> I believe per_cpu variables still use.

The %gs register is not used since the address of the per cpu area is
available as one of the first fields in the per cpu areas.

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/