linux-kernel - Re: [PATCH v2] mempolicy: reduce references to the current

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Message-Id: <20110419093421.9371.A69D9226@jp.fujitsu.com>
Date:	Tue, 19 Apr 2011 09:34:14 +0900 (JST)
From:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
To:	Namhyung Kim <namhyung@...il.com>
Cc:	kosaki.motohiro@...fujitsu.com,
	Minchan Kim <minchan.kim@...il.com>,
	Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] mempolicy: reduce references to the current

> Remove duplicated reference to the 'current' task using a local
> variable. Since refering the current can be a burden, it'd better
> cache the reference, IMHO. At least this saves some bytes on x86_64.
> 
>   $ size mempolicy-{old,new}.o
>      text    data    bss     dec     hex filename
>     25203    2448   9176   36827    8fdb mempolicy-old.o
>     25136    2448   9184   36768    8fa0 mempolicy-new.o
> 
> Signed-off-by: Namhyung Kim <namhyung@...il.com>

But, dense stack usage is also performance good thing. Therefore your
patch benefit is not obvious. I have two request.

1) Please don't increase mess into no hot path. It's no worth.
2) Please mesure performance your box instead size command.

thanks.


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