linux-kernel - Re: [PATCH v4 3/9] net: xfrm: use __this_cpu

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Message-ID: <20121113104839.GJ22290@secunet.com>
Date:	Tue, 13 Nov 2012 11:48:39 +0100
From:	Steffen Klassert <steffen.klassert@...unet.com>
To:	Shan Wei <shanwei88@...il.com>
Cc:	Christoph Lameter <cl@...ux.com>,
	David Miller <davem@...emloft.net>,
	NetDev <netdev@...r.kernel.org>,
	Herbert Xu <herbert@...dor.apana.org.au>,
	Kernel-Maillist <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v4 3/9] net: xfrm: use __this_cpu_read per-cpu helper

On Tue, Nov 13, 2012 at 05:33:19PM +0800, Shan Wei wrote:
> Steffen Klassert said, at 2012/11/13 15:21:
> > 
> > This should just fetch the tfm pointer, so why exactly __this_cpu_read
> > is better than __this_cpu_ptr? Please keep in mind that performance is
> > not the most important thing here. It's much more important that it
> > works in any case.
>  
> [0/9] describes why we should submit this series patches.
> you are not included in original mail.
> 
> this_cpu_ptr relocates and address. this_cpu_read() relocates the address
> and performs the fetch. If you want to operate on rda(defined as per_cpu) 
> then you can only use this_cpu_ptr. this_cpu_read() saves you more instructions
> since it can do the relocation and the fetch in one instruction.
> 

Ok, so please add a commit message to describe your changes.

Thanks.
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