Date: Tue, 13 Jan 2009 13:33:17 +0100
From: Ingo Molnar <mingo@elte.hu>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Ravikiran G Thirumalai <kiran@scalex86.org>,
       Frederik Deweerdt <frederik.deweerdt@xprog.eu>, andi@firstfloor.org,
       tglx@linutronix.de, hpa@zytor.com, linux-kernel@vger.kernel.org
Subject: Re: [patch] tlb flush_data: replace per_cpu with an array
Message-ID: <20090113123317.GA29926@elte.hu>
References: <20090112213539.GA10720@gambetta> <20090112223421.GA20594@localdomain> <20090112230052.GB18771@elte.hu> <1231848016.442.112.camel@twins>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <1231848016.442.112.camel@twins>
User-Agent: Mutt/1.5.18 (2008-05-17)
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 872
Lines: 23


* Peter Zijlstra <peterz@infradead.org> wrote:

> > -	char pad[SMP_CACHE_BYTES];
> > -} ____cacheline_aligned;
> > +	char pad[X86_INTERNODE_CACHE_BYTES];
> > +} ____cacheline_internodealigned_in_smp;
> 
> That will make the below array 8*4096 bytes for VSMP, which pushes the 
> limit for memory savings up to 256 cpus.

VSMP is a clustering solution (default-disabled) that pushes 
L1_CACHE_BYTES to 4096 bytes (4K). That is an extremely large alignment 
that pushes up the BSS size ten-fold (!), so no generic Linux distribution 
enables it. 32K compared to 9MB bloat caused by 4K cachelines is a drop in 
the ocean.

	Ingo
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/