linux-kernel - Re: [PATCH 1/2] Define new percpu interface for shared data -- version 3

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Message-ID: <20070523192005.GB4072@localhost.localdomain>
Date:	Wed, 23 May 2007 12:20:05 -0700
From:	Ravikiran G Thirumalai <kiran@...lex86.org>
To:	"Yu, Fenghua" <fenghua.yu@...el.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	"Siddha, Suresh B" <suresh.b.siddha@...el.com>, clameter@....com,
	rmk@....linux.org.uk, linux-kernel@...r.kernel.org,
	schwidefsky@...ibm.com, heiko.carstens@...ibm.com
Subject: Re: [PATCH 1/2] Define new percpu interface for shared data -- version 3

On Wed, May 23, 2007 at 12:09:56PM -0700, Yu, Fenghua wrote:
> 
> >Has there been any measurable benefit yet due to tail padding?
> 
> We don't have data that tail padding actually helps. It all
> depends on what data the linker lays out in the cachelines.
> 
> As of now we just want to create the infrastructure (so that
> more and more people who need it, can use it).

So what we have now is space wastage on some architectures, space savings on
some, but with no measurable performance benefit due to the infrastructure
itself.  Why not push the infrastructure when we really need it, as against
pushing it now when we are not sure if it benefits?

Thanks,
Kiran 
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