linux-kernel - Re: [GIT PATCH] x86,percpu: fix pageattr handling with remap allocator

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Message-ID: <4A0ED8D8.2010303@kernel.org>
Date:	Sun, 17 May 2009 00:16:40 +0900
From:	Tejun Heo <tj@...nel.org>
To:	suresh.b.siddha@...el.com
CC:	"JBeulich@...ell.com" <JBeulich@...ell.com>,
	"andi@...stfloor.org" <andi@...stfloor.org>,
	"mingo@...e.hu" <mingo@...e.hu>,
	"linux-kernel-owner@...r.kernel.org" 
	<linux-kernel-owner@...r.kernel.org>,
	"hpa@...or.com" <hpa@...or.com>,
	"tglx@...utronix.de" <tglx@...utronix.de>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [GIT PATCH] x86,percpu: fix pageattr handling with remap allocator

Hello, Suresh.

Suresh Siddha wrote:
> Tejun, Can you please educate me why we need to map this first
> percpu chunk (which is pre-allocated during boot and is physically
> contiguous) into vmalloc area?

To make areas for each cpu congruent such that the address offset of a
percpu symbol for CPU N is always the same from the address for CPU 0.

> Perhaps even for the other dynamically allocated secondary chunks?
> (as far as I can see, all the chunk allocations seems to be
> physically contiguous and later mapped into vmalloc area)..
> 
> That should simplify these things quite a bit(atleast for first
> percpu chunk).  I am missing something obvious I guess.

Hmm... Sorry I don't really follow.  Can you please elaborate the
question?

thanks.

-- 
tejun
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