linux-kernel - Re: [patch] block layer: kmemcheck fixes

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Message-Id: <20080207.172246.31415231.davem@davemloft.net>
Date:	Thu, 07 Feb 2008 17:22:46 -0800 (PST)
From:	David Miller <davem@...emloft.net>
To:	torvalds@...ux-foundation.org
Cc:	mingo@...e.hu, jens.axboe@...cle.com, linux-kernel@...r.kernel.org,
	Alan.Brunelle@...com, arjan@...ux.intel.com, dgc@....com,
	npiggin@...e.de, akpm@...ux-foundation.org,
	vegard.nossum@...il.com, penberg@...il.com
Subject: Re: [patch] block layer: kmemcheck fixes

From: Linus Torvalds <torvalds@...ux-foundation.org>
Date: Thu, 7 Feb 2008 09:42:56 -0800 (PST)

> Can we please just stop doing these one-by-one assignments, and just do 
> something like
> 
> 	memset(rq, 0, sizeof(*rq));
> 	rq->q = q;
> 	rq->ref_count = 1;
> 	INIT_HLIST_NODE(&rq->hash);
> 	RB_CLEAR_NODE(&rq->rb_node);
> 
> instead?
> 
> The memset() is likely faster and smaller than one-by-one assignments 
> anyway, even if the one-by-ones can avoid initializing some field or there 
> ends up being a double initialization..

The problem is store buffer compression.  At least a few years
ago this made a huge difference in sk_buff initialization in the
networking.

Maybe cpus these days have so much store bandwith that doing
things like the above is OK, but I doubt it :-)
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