linux-kernel - Re: [PATCH] mm: remove global locks from mm/highmem.c

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Message-ID: <45BE9FE8.4080603@mbligh.org>
Date:	Mon, 29 Jan 2007 17:31:20 -0800
From:	"Martin J. Bligh" <mbligh@...igh.org>
To:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc:	Andrew Morton <akpm@...l.org>, linux-kernel@...r.kernel.org,
	linux-mm@...ck.org, Ingo Molnar <mingo@...e.hu>
Subject: Re: [PATCH] mm: remove global locks from mm/highmem.c

Peter Zijlstra wrote:
> On Sun, 2007-01-28 at 14:29 -0800, Andrew Morton wrote:
> 
>> As Christoph says, it's very much preferred that code be migrated over to
>> kmap_atomic().  Partly because kmap() is deadlockable in situations where a
>> large number of threads are trying to take two kmaps at the same time and
>> we run out.  This happened in the past, but incidences have gone away,
>> probably because of kmap->kmap_atomic conversions.
> 
>> From which callsite have you measured problems?
> 
> CONFIG_HIGHPTE code in -rt was horrid. I'll do some measurements on
> mainline.
> 

CONFIG_HIGHPTE is always horrid -we've known that for years.
Don't use it.

If that's all we're fixing here, I'd be highly suspect ...

M.

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