linux-kernel - Re: [PATCH UPDATED] percpu: use dynamic percpu allocator as the default percpu allocator

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Date:	Wed, 01 Apr 2009 09:15:05 +0900
From:	Tejun Heo <tj@...nel.org>
To:	Christoph Lameter <cl@...ux.com>
CC:	Ingo Molnar <mingo@...e.hu>,
	Martin Schwidefsky <schwidefsky@...ibm.com>,
	rusty@...tcorp.com.au, tglx@...utronix.de, x86@...nel.org,
	linux-kernel@...r.kernel.org, hpa@...or.com,
	Paul Mundt <lethal@...ux-sh.org>, rmk@....linux.org.uk,
	starvik@...s.com, ralf@...ux-mips.org, davem@...emloft.net,
	cooloney@...nel.org, kyle@...artin.ca, matthew@....cx,
	grundler@...isc-linux.org, takata@...ux-m32r.org,
	benh@...nel.crashing.org, rth@...ddle.net,
	ink@...assic.park.msu.ru, heiko.carstens@...ibm.com,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Nick Piggin <npiggin@...e.de>
Subject: Re: [PATCH UPDATED] percpu: use dynamic percpu allocator as the default
 percpu allocator

Hello,

Christoph Lameter wrote:
> I reviewed the new per cpu allocator. Quite extensive work. Found two
> issues that I would like to have addressed. But basically:
> 
> Reviewed-by: Christoph Lameter <cl@...ux.com>

Thanks.

> Two issues
> 
> 1. Lot of unnecessary use of __read_mostly for local static variables that
> are not on the hotpath. Patch follows in this message.

Hmmm... Those are basically read-only vars once initialization is
complete.  IIUC, __read_mostly just puts the tagged variables into a
separate segment so that they don't have to worry about cacheline
bouncing.  Is there any reason to remove __read_mostly?  Or is it just
that it's mostly superflous?

> 2. rbtree is not necessary since we can link back through the an available
> field in struct page. Patch in next message.

Ah... nice.  I was thinking about adding ->private pointer to the
vmalloc structure but if page already has the space, all the better.

Thanks.

-- 
tejun
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