linux-kernel - Re: [Linaro-mm-sig] [PATCH 08/10] mm: cma: Contiguous Memory Allocator added

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Message-ID: <20110616170133.GC28032@labbmf-linux.qualcomm.com>
Date:	Thu, 16 Jun 2011 10:01:33 -0700
From:	Larry Bassel <lbassel@...eaurora.org>
To:	Arnd Bergmann <arnd@...db.de>
Cc:	Larry Bassel <lbassel@...eaurora.org>,
	Marek Szyprowski <m.szyprowski@...sung.com>,
	'Zach Pfeffer' <zach.pfeffer@...aro.org>,
	'Daniel Walker' <dwalker@...eaurora.org>,
	'Daniel Stone' <daniels@...labora.com>,
	'Jesse Barker' <jesse.barker@...aro.org>,
	'Mel Gorman' <mel@....ul.ie>,
	'KAMEZAWA Hiroyuki' <kamezawa.hiroyu@...fujitsu.com>,
	linux-kernel@...r.kernel.org,
	'Michal Nazarewicz' <mina86@...a86.com>,
	linaro-mm-sig@...ts.linaro.org, linux-mm@...ck.org,
	'Kyungmin Park' <kyungmin.park@...sung.com>,
	'Ankita Garg' <ankita@...ibm.com>,
	'Andrew Morton' <akpm@...ux-foundation.org>,
	linux-arm-kernel@...ts.infradead.org, linux-media@...r.kernel.org
Subject: Re: [Linaro-mm-sig] [PATCH 08/10] mm: cma: Contiguous Memory
 Allocator added

On 16 Jun 11 00:06, Arnd Bergmann wrote:
> On Wednesday 15 June 2011 23:39:58 Larry Bassel wrote:
> > On 15 Jun 11 10:36, Marek Szyprowski wrote:
> > > On Tuesday, June 14, 2011 10:42 PM Arnd Bergmann wrote:
> > > 
> > > > On Tuesday 14 June 2011 20:58:25 Zach Pfeffer wrote:
> > > > > I've seen this split bank allocation in Qualcomm and TI SoCs, with
> > > > > Samsung, that makes 3 major SoC vendors (I would be surprised if
> > > > > Nvidia didn't also need to do this) - so I think some configurable
> > > > > method to control allocations is necessarily. The chips can't do
> > > > > decode without it (and by can't do I mean 1080P and higher decode is
> > > > > not functionally useful). Far from special, this would appear to be
> > > > > the default.
> > 
> > We at Qualcomm have some platforms that have memory of different
> > performance characteristics, some drivers will need a way of
> > specifying that they need fast memory for an allocation (and would prefer
> > an error if it is not available rather than a fallback to slower
> > memory). It would also be bad if allocators who don't need fast
> > memory got it "accidentally", depriving those who really need it.
> 
> Can you describe how the memory areas differ specifically?
> Is there one that is always faster but very small, or are there
> just specific circumstances under which some memory is faster than
> another?

One is always faster, but very small (generally 2-10% the size
of "normal" memory).

Larry

-- 
Sent by an employee of the Qualcomm Innovation Center, Inc.
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum.
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