linux-kernel - Re: What was the problem with quicklists and x86-64?

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Message-ID: <Pine.LNX.4.64.0712131251300.18314@schroedinger.engr.sgi.com>
Date:	Thu, 13 Dec 2007 12:53:11 -0800 (PST)
From:	Christoph Lameter <clameter@....com>
To:	Benjamin Herrenschmidt <benh@...nel.crashing.org>
cc:	Jeremy Fitzhardinge <jeremy@...p.org>,
	Suresh Siddha <suresh.b.siddha@...el.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Ingo Molnar <mingo@...e.hu>, Andi Kleen <ak@...e.de>,
	Tony Luck <tony.luck@...el.com>,
	Asit Mallick <asit.k.mallick@...el.com>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: What was the problem with quicklists and x86-64?

On Fri, 14 Dec 2007, Benjamin Herrenschmidt wrote:

> > These issues only exist with NUMA because of the freeing of off node pages 
> > before the TLB flush was done. There was a discussion about this issue and 
> > my fix of simply not freeing the offnode pages early was ignored. Instead 
> > the x86_64 implementation (which has no problems that I know of) was 
> > pulled leaving the issue open in the core. Benjamin Herrrenschmidt 
> > wanted to take a look at these issues (CCing him).
> 
> I don't know how NUMA gets in the picture there, it's probably very x86
> specific thing. The issue we have here happens on other platforms
> unrelated to NUMA. The fact that is tired to NUMA on x86 might be due to
> the way the HW tablewalk operates on these. 

This is a generic NUMA issue here! Quicklist pages that are not on 
the current node are freed without waiting for the TLB flush. The patch 
that I posted fixes that by requiring that all pages be flushed. 
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