Messages in this thread | | | Date | Thu, 15 Jan 2015 21:28:26 -0600 (CST) | From | Christoph Lameter <> | Subject | Re: [PATCH v2 1/2] mm/slub: optimize alloc/free fastpath by removing preemption on/off |
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On Thu, 15 Jan 2015, Andrew Morton wrote:
> > I saw roughly 5% win in a fast-path loop over kmem_cache_alloc/free > > in CONFIG_PREEMPT. (14.821 ns -> 14.049 ns) > > I'm surprised. preempt_disable/enable are pretty fast. I wonder why > this makes a measurable difference. Perhaps preempt_enable()'s call to > preempt_schedule() added pain?
The rest of the fastpath is already highly optimized. That is why something like preempt enable/disable has such a disproportionate effect.
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