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

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Message-ID: <alpine.DEB.2.11.1501152155480.14236@gentwo.org>
Date:	Thu, 15 Jan 2015 21:57:58 -0600 (CST)
From:	Christoph Lameter <cl@...ux.com>
To:	Steven Rostedt <rostedt@...dmis.org>
cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Joonsoo Kim <iamjoonsoo.kim@....com>,
	Pekka Enberg <penberg@...nel.org>,
	David Rientjes <rientjes@...gle.com>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org,
	Jesper Dangaard Brouer <brouer@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Peter Zijlstra <peterz@...radead.org>
Subject: Re: [PATCH v2 1/2] mm/slub: optimize alloc/free fastpath by removing
 preemption on/off

> I get:
>
> 		mov    %gs:0x18(%rax),%rdx
>
> Looks to me that %gs is used.

%gs is used as a segment prefix. That does not add significant cycles.
Retrieving the content of %gs and loading it into another register would
be expensive in terms of cpu cycles.

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