linux-kernel - Re: [PATCH 2/3] slub: Support for array operations

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Date:	Wed, 11 Feb 2015 20:46:53 -0600 (CST)
From:	Christoph Lameter <cl@...ux.com>
To:	Jesper Dangaard Brouer <brouer@...hat.com>
cc:	akpm@...uxfoundation.org, linux-kernel@...r.kernel.org,
	linux-mm@...ck.org, penberg@...nel.org, iamjoonsoo@....com
Subject: Re: [PATCH 2/3] slub: Support for array operations

On Thu, 12 Feb 2015, Jesper Dangaard Brouer wrote:

> Measured on my laptop CPU i7-2620M CPU @ 2.70GHz:
>
>  * 12.775 ns - "clean" spin_lock_unlock
>  * 21.099 ns - irqsave variant spinlock
>  * 22.808 ns - "manual" irqsave before spin_lock
>  * 14.618 ns - "manual" local_irq_disable + spin_lock
>
> Reproducible via my github repo:
>  https://github.com/netoptimizer/prototype-kernel/blob/master/kernel/lib/time_bench_sample.c
>
> The clean spin_lock_unlock is 8.324 ns faster than irqsave variant.
> The irqsave variant is actually faster than expected, as the measurement
> of an isolated local_irq_save_restore were 13.256 ns.

I am using spin_lock_irq() in the current version on my system. If the
performance of that is a problem then please optimize that function.
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