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From: Arnd Bergmann <arnd@arndb.de>
To: linaro-mm-sig@lists.linaro.org
Cc: Nicolas Pitre <nicolas.pitre@linaro.org>,
	"'Daniel Walker'" <dwalker@codeaurora.org>,
	"Russell King - ARM Linux" <linux@arm.linux.org.uk>,
	linux-media@vger.kernel.org, "'Jonathan Corbet'" <corbet@lwn.net>,
	"'Mel Gorman'" <mel@csn.ul.ie>,
	"'Chunsang Jeong'" <chunsang.jeong@linaro.org>,
	lkml <linux-kernel@vger.kernel.org>,
	"'Michal Nazarewicz'" <mina86@mina86.com>,
	"'Jesse Barker'" <jesse.barker@linaro.org>,
	"'Kyungmin Park'" <kyungmin.park@samsung.com>,
	"'KAMEZAWA Hiroyuki'" <kamezawa.hiroyu@jp.fujitsu.com>,
	"'Andrew Morton'" <akpm@linux-foundation.org>,
	linux-mm@kvack.org, linux-arm-kernel@lists.infradead.org,
	"'Ankita Garg'" <ankita@in.ibm.com>
Subject: Re: [Linaro-mm-sig] [PATCH 6/8] drivers: add Contiguous Memory Allocator
Date: Wed, 6 Jul 2011 22:23:01 +0200	[thread overview]
Message-ID: <201107062223.01940.arnd@arndb.de> (raw)
In-Reply-To: <alpine.LFD.2.00.1107061459520.14596@xanadu.home>

On Wednesday 06 July 2011 21:10:07 Nicolas Pitre wrote:
> If you get a highmem page, because the cache is VIPT, that page might 
> still be cached even if it wasn't mapped.  With a VIVT cache we must 
> flush the cache whenever a highmem page is unmapped.  There is no such 
> restriction with VIPT i.e. ARMv6 and above.  Therefore to make sure the 
> highmem page you get doesn't have cache lines associated to it, you must 
> first map it cacheable, then perform cache invalidation on it, and 
> eventually remap it as non-cacheable.  This is necessary because there 
> is no way to perform cache maintenance on L1 cache using physical 
> addresses unfortunately.  See commit 7e5a69e83b for an example of what 
> this entails (fortunately commit 3e4d3af501 made things much easier and 
> therefore commit 39af22a79 greatly simplified things).

Ok, thanks for the explanation. This definitely makes the highmem approach
much harder to get right, and slower. Let's hope then that Marek's approach
of using small pages for the contiguous memory region and changing their
attributes on the fly works out better than this.

	Arnd

  reply	other threads:[~2011-07-06 20:23 UTC|newest]

Thread overview: 59+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2011-07-05  7:41 [PATCHv11 0/8] Contiguous Memory Allocator Marek Szyprowski
2011-07-05  7:41 ` [PATCH 1/8] mm: move some functions from memory_hotplug.c to page_isolation.c Marek Szyprowski
2011-07-05 11:27   ` Arnd Bergmann
2011-07-05  7:41 ` [PATCH 2/8] mm: alloc_contig_freed_pages() added Marek Szyprowski
2011-07-05 11:30   ` Arnd Bergmann
2011-07-05  7:41 ` [PATCH 3/8] mm: alloc_contig_range() added Marek Szyprowski
2011-07-05 11:31   ` Arnd Bergmann
2011-07-05  7:41 ` [PATCH 4/8] mm: MIGRATE_CMA migration type added Marek Szyprowski
2011-07-05 11:44   ` Arnd Bergmann
2011-07-05 12:27     ` Russell King - ARM Linux
2011-07-05  7:41 ` [PATCH 5/8] mm: MIGRATE_CMA isolation functions added Marek Szyprowski
2011-07-05 11:45   ` Arnd Bergmann
2011-07-05  7:41 ` [PATCH 6/8] drivers: add Contiguous Memory Allocator Marek Szyprowski
2011-07-05 10:24   ` Marek Szyprowski
2011-07-05 11:02   ` [PATCH 6/8 RESEND] " Marek Szyprowski
2011-07-05 11:50     ` Arnd Bergmann
2011-07-05 11:33   ` [PATCH 6/8] " Russell King - ARM Linux
2011-07-05 12:27     ` Arnd Bergmann
2011-07-05 12:30       ` Russell King - ARM Linux
2011-07-05 13:58         ` Arnd Bergmann
2011-07-08 17:25           ` Russell King - ARM Linux
2011-07-12 13:39             ` Arnd Bergmann
2011-08-03 17:43       ` James Bottomley
2011-09-26 12:06         ` Marek Szyprowski
2011-09-26 13:00         ` Russell King - ARM Linux
2011-07-06 13:58     ` Marek Szyprowski
2011-07-06 14:09       ` Arnd Bergmann
2011-07-06 14:23         ` Russell King - ARM Linux
2011-07-06 14:37           ` [Linaro-mm-sig] " Nicolas Pitre
2011-07-06 14:59             ` Arnd Bergmann
2011-07-09 14:57               ` Janusz Krzysztofik
2011-07-11 13:47                 ` Marek Szyprowski
2011-07-11 19:01                   ` Janusz Krzysztofik
2011-07-12  5:34                     ` Marek Szyprowski
2011-07-06 14:51           ` Arnd Bergmann
2011-07-06 15:48             ` Russell King - ARM Linux
2011-07-06 16:05               ` Christoph Lameter
2011-07-06 16:09                 ` Michal Nazarewicz
2011-07-06 16:19                   ` Christoph Lameter
2011-07-06 17:15                     ` Russell King - ARM Linux
2011-07-06 19:03                       ` Christoph Lameter
2011-07-06 17:02                 ` Russell King - ARM Linux
2011-07-06 16:31               ` Arnd Bergmann
2011-07-06 19:10                 ` Nicolas Pitre
2011-07-06 20:23                   ` Arnd Bergmann [this message]
2011-07-07  5:29                     ` [Linaro-mm-sig] " Nicolas Pitre
2011-07-06 14:56         ` Marek Szyprowski
2011-07-06 15:37           ` Russell King - ARM Linux
2011-07-06 15:47             ` Marek Szyprowski
2011-07-14 12:29   ` Marek Szyprowski
2011-07-05  7:41 ` [PATCH 7/8] ARM: integrate CMA with dma-mapping subsystem Marek Szyprowski
2011-07-05 11:50   ` Arnd Bergmann
2011-07-05  7:41 ` [PATCH 8/8] ARM: S5PV210: example of CMA private area for FIMC device on Goni board Marek Szyprowski
2011-07-05 11:51   ` Arnd Bergmann
2011-07-05 12:07 ` [PATCHv11 0/8] Contiguous Memory Allocator Arnd Bergmann
2011-07-05 12:28   ` Russell King - ARM Linux
2011-07-06 22:11   ` Andrew Morton
2011-07-07  7:36     ` Arnd Bergmann
2011-07-11 13:24     ` Marek Szyprowski

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