From mboxrd@z Thu Jan 1 00:00:00 1970 From: minchan@kernel.org (Minchan Kim) Date: Mon, 16 Apr 2012 10:32:41 +0900 Subject: [PATCH 4/4] ARM: remove consistent dma region and use common vmalloc range for dma allocations In-Reply-To: <20120413183813.GO24211@n2100.arm.linux.org.uk> References: <1334325950-7881-1-git-send-email-m.szyprowski@samsung.com> <1334325950-7881-5-git-send-email-m.szyprowski@samsung.com> <20120413183813.GO24211@n2100.arm.linux.org.uk> Message-ID: <4F8B76B9.1060505@kernel.org> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On 04/14/2012 03:38 AM, Russell King - ARM Linux wrote: > On Fri, Apr 13, 2012 at 04:05:50PM +0200, Marek Szyprowski wrote: >> This patch changes dma-mapping subsystem to use generic vmalloc areas >> for all consistent dma allocations. This increases the total size limit >> of the consistent allocations and removes platform hacks and a lot of >> duplicated code. > > NAK. I don't think you appreciate the contexts from which the dma coherent > code can be called from, and the reason why we pre-allocate the page > tables (so that IRQ-based allocations work.) > > The vmalloc region doesn't allow that because page tables are allocated > using GFP_KERNEL not GFP_ATOMIC. > > Sorry. > Off-topic. I don't know why vmalloc functions have gfp_t argument. As Russel pointed out, we allocates page tables with GFP_KERNEL regardless of gfp_t passed. It means gfp_t passed is useless. I see there are many cases calling __vmalloc with GFP_NOFS, even GFP_ATOMIC. Then, it could end up deadlocking in reclaim context or schedule bug. I'm not sure why we can't see such bugs until now. If I didn't miss something, Shouldn't we fix it? > -- > To unsubscribe, send a message with 'unsubscribe linux-mm' in > the body to majordomo at 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 at kvack.org > From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx141.postini.com [74.125.245.141]) by kanga.kvack.org (Postfix) with SMTP id 0C0136B004D for ; Sun, 15 Apr 2012 21:32:45 -0400 (EDT) Message-ID: <4F8B76B9.1060505@kernel.org> Date: Mon, 16 Apr 2012 10:32:41 +0900 From: Minchan Kim MIME-Version: 1.0 Subject: Re: [PATCH 4/4] ARM: remove consistent dma region and use common vmalloc range for dma allocations References: <1334325950-7881-1-git-send-email-m.szyprowski@samsung.com> <1334325950-7881-5-git-send-email-m.szyprowski@samsung.com> <20120413183813.GO24211@n2100.arm.linux.org.uk> In-Reply-To: <20120413183813.GO24211@n2100.arm.linux.org.uk> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Russell King - ARM Linux , Andrew Morton , KAMEZAWA Hiroyuki , Rik van Riel , Hugh Dickins , Mel Gorman , Johannes Weiner Cc: Marek Szyprowski , linux-arm-kernel@lists.infradead.org, linaro-mm-sig@lists.linaro.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Kyungmin Park , Arnd Bergmann , Chunsang Jeong , Krishna Reddy , Konrad Rzeszutek Wilk , Hiroshi Doyu , Subash Patel On 04/14/2012 03:38 AM, Russell King - ARM Linux wrote: > On Fri, Apr 13, 2012 at 04:05:50PM +0200, Marek Szyprowski wrote: >> This patch changes dma-mapping subsystem to use generic vmalloc areas >> for all consistent dma allocations. This increases the total size limit >> of the consistent allocations and removes platform hacks and a lot of >> duplicated code. > > NAK. I don't think you appreciate the contexts from which the dma coherent > code can be called from, and the reason why we pre-allocate the page > tables (so that IRQ-based allocations work.) > > The vmalloc region doesn't allow that because page tables are allocated > using GFP_KERNEL not GFP_ATOMIC. > > Sorry. > Off-topic. I don't know why vmalloc functions have gfp_t argument. As Russel pointed out, we allocates page tables with GFP_KERNEL regardless of gfp_t passed. It means gfp_t passed is useless. I see there are many cases calling __vmalloc with GFP_NOFS, even GFP_ATOMIC. Then, it could end up deadlocking in reclaim context or schedule bug. I'm not sure why we can't see such bugs until now. If I didn't miss something, Shouldn't we fix it? > -- > 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 > -- 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 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752682Ab2DPBcr (ORCPT ); Sun, 15 Apr 2012 21:32:47 -0400 Received: from LGEMRELSE6Q.lge.com ([156.147.1.121]:48907 "EHLO LGEMRELSE6Q.lge.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752545Ab2DPBcq (ORCPT ); Sun, 15 Apr 2012 21:32:46 -0400 X-AuditID: 9c930179-b7b2cae000000ca1-00-4f8b76bbc5f9 Message-ID: <4F8B76B9.1060505@kernel.org> Date: Mon, 16 Apr 2012 10:32:41 +0900 From: Minchan Kim User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:11.0) Gecko/20120410 Thunderbird/11.0.1 MIME-Version: 1.0 Newsgroups: gmane.linux.kernel.mm,gmane.linux.ports.arm.kernel,gmane.linux.kernel To: Russell King - ARM Linux , Andrew Morton , KAMEZAWA Hiroyuki , Rik van Riel , Hugh Dickins , Mel Gorman , Johannes Weiner CC: Marek Szyprowski , linux-arm-kernel@lists.infradead.org, linaro-mm-sig@lists.linaro.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Kyungmin Park , Arnd Bergmann , Chunsang Jeong , Krishna Reddy , Konrad Rzeszutek Wilk , Hiroshi Doyu , Subash Patel Subject: Re: [PATCH 4/4] ARM: remove consistent dma region and use common vmalloc range for dma allocations References: <1334325950-7881-1-git-send-email-m.szyprowski@samsung.com> <1334325950-7881-5-git-send-email-m.szyprowski@samsung.com> <20120413183813.GO24211@n2100.arm.linux.org.uk> In-Reply-To: <20120413183813.GO24211@n2100.arm.linux.org.uk> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit X-Brightmail-Tracker: AAAAAA== Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 04/14/2012 03:38 AM, Russell King - ARM Linux wrote: > On Fri, Apr 13, 2012 at 04:05:50PM +0200, Marek Szyprowski wrote: >> This patch changes dma-mapping subsystem to use generic vmalloc areas >> for all consistent dma allocations. This increases the total size limit >> of the consistent allocations and removes platform hacks and a lot of >> duplicated code. > > NAK. I don't think you appreciate the contexts from which the dma coherent > code can be called from, and the reason why we pre-allocate the page > tables (so that IRQ-based allocations work.) > > The vmalloc region doesn't allow that because page tables are allocated > using GFP_KERNEL not GFP_ATOMIC. > > Sorry. > Off-topic. I don't know why vmalloc functions have gfp_t argument. As Russel pointed out, we allocates page tables with GFP_KERNEL regardless of gfp_t passed. It means gfp_t passed is useless. I see there are many cases calling __vmalloc with GFP_NOFS, even GFP_ATOMIC. Then, it could end up deadlocking in reclaim context or schedule bug. I'm not sure why we can't see such bugs until now. If I didn't miss something, Shouldn't we fix it? > -- > 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 >