linux-kernel - Re: [tip:core/locking 2/3] lockdep:define preallocated "stack" for BFS as per cpu variable

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Date:	Wed, 22 Jul 2009 15:19:15 +0200
From:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
To:	Ming Lei <tom.leiming@...il.com>
Cc:	linux-kernel@...r.kernel.org, akpm@...ux-foundation.org,
	mingo@...e.hu, torvalds@...ux-foundation.org
Subject: Re: [tip:core/locking 2/3] lockdep:define preallocated "stack" for
  BFS as per cpu variable

On Wed, 2009-07-22 at 21:10 +0800, Ming Lei wrote:
> 2009/7/22 Peter Zijlstra <a.p.zijlstra@...llo.nl>:
> > On Wed, 2009-07-22 at 20:58 +0800, tom.leiming@...il.com wrote:
> >> From: Ming Lei <tom.leiming@...il.com>
> >
> > This patch can use a changelog.
> >
> > Why is this needed, isn't all that serialized by the graph_lock anyway?
> > Or are there a few paths where this isn't the case and we're now racy?
> 
> It is really serialized by the graph_lock, but we can prevent cpu cache from
> being flushing by different cpu access,  which seems that can be avoided by
> per cpu variables. Right?

I doubt it'll make a difference, got any numbers to back that up?

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