linux-kernel - Re: [PATCH 3/4]percpu_counter: fix code for 32bit systems

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Message-ID: <20110413040013.GB24161@mtj.dyndns.org>
Date:	Wed, 13 Apr 2011 13:00:13 +0900
From:	"tj@...nel.org" <tj@...nel.org>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	Shaohua Li <shaohua.li@...el.com>,
	lkml <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"cl@...ux.com" <cl@...ux.com>
Subject: Re: [PATCH 3/4]percpu_counter: fix code for 32bit systems

Hello,

On Wed, Apr 13, 2011 at 05:53:40AM +0200, Eric Dumazet wrote:
> Le mercredi 13 avril 2011 à 11:03 +0800, Shaohua Li a écrit :
> > I can do this, but please give a reason. If network code is the only
> > place requiring disable irq, why not network code do it?
> 
> Lot of percpu_counter users dont use full s64 range, but "unsigned long"
> or "unsigned int". Adding a lock on 32bit arches to get the s64, then
> truncate it is not needed.

Yeah, it might hurt 32bit archs a bit but if 64bit becomes better I'll
take that any day.  Also, atomic64_t implementation on x86-32 seems
pretty good and doesn't depend on irq spinlocks (which is quite
expensive), so it shouldn't be too bad.

Thanks.

-- 
tejun
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