From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752704Ab1FNRMq (ORCPT ); Tue, 14 Jun 2011 13:12:46 -0400 Received: from bhuna.collabora.co.uk ([93.93.128.226]:45903 "EHLO bhuna.collabora.co.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751410Ab1FNRMm (ORCPT ); Tue, 14 Jun 2011 13:12:42 -0400 X-Greylist: delayed 642 seconds by postgrey-1.27 at vger.kernel.org; Tue, 14 Jun 2011 13:12:42 EDT Date: Tue, 14 Jun 2011 18:01:58 +0100 From: Daniel Stone To: Arnd Bergmann Cc: Michal Nazarewicz , "'Ankita Garg'" , "'Daniel Walker'" , "'Jesse Barker'" , "'Mel Gorman'" , linux-kernel@vger.kernel.org, linaro-mm-sig@lists.linaro.org, linux-mm@kvack.org, "'Kyungmin Park'" , "'KAMEZAWA Hiroyuki'" , "'Andrew Morton'" , linux-arm-kernel@lists.infradead.org, linux-media@vger.kernel.org Subject: Re: [Linaro-mm-sig] [PATCH 08/10] mm: cma: Contiguous Memory Allocator added Message-ID: <20110614170158.GU2419@fooishbar.org> Mail-Followup-To: Daniel Stone , Arnd Bergmann , Michal Nazarewicz , 'Ankita Garg' , 'Daniel Walker' , 'Jesse Barker' , 'Mel Gorman' , linux-kernel@vger.kernel.org, linaro-mm-sig@lists.linaro.org, linux-mm@kvack.org, 'Kyungmin Park' , 'KAMEZAWA Hiroyuki' , 'Andrew Morton' , linux-arm-kernel@lists.infradead.org, linux-media@vger.kernel.org References: <1307699698-29369-1-git-send-email-m.szyprowski@samsung.com> <201106141549.29315.arnd@arndb.de> <201106141803.00876.arnd@arndb.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <201106141803.00876.arnd@arndb.de> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, On Tue, Jun 14, 2011 at 06:03:00PM +0200, Arnd Bergmann wrote: > On Tuesday 14 June 2011, Michal Nazarewicz wrote: > > On Tue, 14 Jun 2011 15:49:29 +0200, Arnd Bergmann wrote: > > > Please explain the exact requirements that lead you to defining multiple > > > contexts. > > > > Some devices may have access only to some banks of memory. Some devices > > may use different banks of memory for different purposes. > > For all I know, that is something that is only true for a few very special > Samsung devices, and is completely unrelated of the need for contiguous > allocations, so this approach becomes pointless as soon as the next > generation of that chip grows an IOMMU, where we don't handle the special > bank attributes. Also, the way I understood the situation for the Samsung > SoC during the Budapest discussion, it's only a performance hack, not a > functional requirement, unless you count '1080p playback' as a functional > requirement. Hm, I think that was something similar but not quite the same: talking about having allocations split to lie between two banks of RAM to maximise the read/write speed for performance reasons. That's something that can be handled in the allocator, rather than an API constraint, as this is. Not that I know of any hardware which is limited as such, but eh. Cheers, Daniel From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail172.messagelabs.com (mail172.messagelabs.com [216.82.254.3]) by kanga.kvack.org (Postfix) with ESMTP id 702E46B0012 for ; Tue, 14 Jun 2011 13:02:04 -0400 (EDT) Date: Tue, 14 Jun 2011 18:01:58 +0100 From: Daniel Stone Subject: Re: [Linaro-mm-sig] [PATCH 08/10] mm: cma: Contiguous Memory Allocator added Message-ID: <20110614170158.GU2419@fooishbar.org> References: <1307699698-29369-1-git-send-email-m.szyprowski@samsung.com> <201106141549.29315.arnd@arndb.de> <201106141803.00876.arnd@arndb.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <201106141803.00876.arnd@arndb.de> Sender: owner-linux-mm@kvack.org List-ID: To: Arnd Bergmann Cc: Michal Nazarewicz , 'Ankita Garg' , 'Daniel Walker' , 'Jesse Barker' , 'Mel Gorman' , linux-kernel@vger.kernel.org, linaro-mm-sig@lists.linaro.org, linux-mm@kvack.org, 'Kyungmin Park' , 'KAMEZAWA Hiroyuki' , 'Andrew Morton' , linux-arm-kernel@lists.infradead.org, linux-media@vger.kernel.org Hi, On Tue, Jun 14, 2011 at 06:03:00PM +0200, Arnd Bergmann wrote: > On Tuesday 14 June 2011, Michal Nazarewicz wrote: > > On Tue, 14 Jun 2011 15:49:29 +0200, Arnd Bergmann wrote: > > > Please explain the exact requirements that lead you to defining multiple > > > contexts. > > > > Some devices may have access only to some banks of memory. Some devices > > may use different banks of memory for different purposes. > > For all I know, that is something that is only true for a few very special > Samsung devices, and is completely unrelated of the need for contiguous > allocations, so this approach becomes pointless as soon as the next > generation of that chip grows an IOMMU, where we don't handle the special > bank attributes. Also, the way I understood the situation for the Samsung > SoC during the Budapest discussion, it's only a performance hack, not a > functional requirement, unless you count '1080p playback' as a functional > requirement. Hm, I think that was something similar but not quite the same: talking about having allocations split to lie between two banks of RAM to maximise the read/write speed for performance reasons. That's something that can be handled in the allocator, rather than an API constraint, as this is. Not that I know of any hardware which is limited as such, but eh. Cheers, Daniel -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org From mboxrd@z Thu Jan 1 00:00:00 1970 From: daniels@collabora.com (Daniel Stone) Date: Tue, 14 Jun 2011 18:01:58 +0100 Subject: [Linaro-mm-sig] [PATCH 08/10] mm: cma: Contiguous Memory Allocator added In-Reply-To: <201106141803.00876.arnd@arndb.de> References: <1307699698-29369-1-git-send-email-m.szyprowski@samsung.com> <201106141549.29315.arnd@arndb.de> <201106141803.00876.arnd@arndb.de> Message-ID: <20110614170158.GU2419@fooishbar.org> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org Hi, On Tue, Jun 14, 2011 at 06:03:00PM +0200, Arnd Bergmann wrote: > On Tuesday 14 June 2011, Michal Nazarewicz wrote: > > On Tue, 14 Jun 2011 15:49:29 +0200, Arnd Bergmann wrote: > > > Please explain the exact requirements that lead you to defining multiple > > > contexts. > > > > Some devices may have access only to some banks of memory. Some devices > > may use different banks of memory for different purposes. > > For all I know, that is something that is only true for a few very special > Samsung devices, and is completely unrelated of the need for contiguous > allocations, so this approach becomes pointless as soon as the next > generation of that chip grows an IOMMU, where we don't handle the special > bank attributes. Also, the way I understood the situation for the Samsung > SoC during the Budapest discussion, it's only a performance hack, not a > functional requirement, unless you count '1080p playback' as a functional > requirement. Hm, I think that was something similar but not quite the same: talking about having allocations split to lie between two banks of RAM to maximise the read/write speed for performance reasons. That's something that can be handled in the allocator, rather than an API constraint, as this is. Not that I know of any hardware which is limited as such, but eh. Cheers, Daniel