linux-kernel - Re: [PATCH v2 -mm 8/9] netconsole: Support multiple logging targets

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Message-ID: <Pine.LNX.4.64.0707110340370.2445@cselinux1.cse.iitk.ac.in>
Date:	Wed, 11 Jul 2007 03:47:09 +0530 (IST)
From:	Satyam Sharma <ssatyam@....iitk.ac.in>
To:	Duane Griffin <duaneg@...da.com>
cc:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Matt Mackall <mpm@...enic.com>,
	Keiichi Kii <k-keiichi@...jp.nec.com>,
	Netdev <netdev@...r.kernel.org>,
	Joel Becker <joel.becker@...cle.com>,
	Stephen Hemminger <shemminger@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	David Miller <davem@...emloft.net>
Subject: Re: [PATCH v2 -mm 8/9] netconsole: Support multiple logging targets

Hi,

On Tue, 10 Jul 2007, Duane Griffin wrote:
> On 10/07/07, Satyam Sharma <ssatyam@....iitk.ac.in> wrote:
> > +       /* Avoid taking lock and disabling interrupts unnecessarily */
> > +       if (unlikely(list_empty(&target_list)))
> > +               return;
> 
> Is the unlikely a good idea here? Not having any targets may be
> unusual but it isn't ridiculous. It might even be a sensible default
> for distros.

Hmm, I put it in there because I expected that the user must have had
at least one target configured (added to target_list) if he's got the
module loaded/built-in (and netconsole registered), which is when this
function would be triggered anyway.

> My (very limited) understanding of unlikely is that it
> could impose a very large penalty in that case and would make a very
> marginal difference at best in the common case.

I wouldn't call it a large penalty, but yeah, probably the unlikely()
there isn't all that important either.

Satyam
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