From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx155.postini.com [74.125.245.155]) by kanga.kvack.org (Postfix) with SMTP id 273B66B0008 for ; Wed, 23 Jan 2013 09:39:22 -0500 (EST) Message-ID: <50FFF5C0.60000@web.de> Date: Wed, 23 Jan 2013 15:37:52 +0100 From: Soeren Moch MIME-Version: 1.0 Subject: Re: [PATCH v2] mm: dmapool: use provided gfp flags for all dma_alloc_coherent() calls References: <20121119144826.f59667b2.akpm@linux-foundation.org> <201301211855.25455.arnd@arndb.de> <20130121210150.GA9184@kroah.com> <201301221813.57741.arnd@arndb.de> In-Reply-To: <201301221813.57741.arnd@arndb.de> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Arnd Bergmann Cc: Greg KH , Jason Cooper , Thomas Petazzoni , Andrew Lunn , KAMEZAWA Hiroyuki , linux-kernel@vger.kernel.org, Michal Hocko , linux-mm@kvack.org, Kyungmin Park , Mel Gorman , Andrew Morton , Marek Szyprowski , linaro-mm-sig@lists.linaro.org, linux-arm-kernel@lists.infradead.org, Sebastian Hesselbarth On 22.01.2013 19:13, Arnd Bergmann wrote: > On Monday 21 January 2013, Greg KH wrote: >>> >>> I don't know a lot about USB, but I always assumed that this was not >>> a normal condition and that there are only a couple of URBs per endpoint >>> used at a time. Maybe Greg or someone else with a USB background can >>> shed some light on this. >> >> There's no restriction on how many URBs a driver can have outstanding at >> once, and if you have a system with a lot of USB devices running at the >> same time, there could be lots of URBs in flight depending on the number >> of host controllers and devices and drivers being used. I only use one host controller and (in this test) two usb devices with the same driver. > Ok, thanks for clarifying that. I read some more of the em28xx driver, > and while it does have a bunch of URBs in flight, there are only five > audio and five video URBs that I see simultaneously being submitted, > and then resubmitted from their completion handlers. I think this > means that there should be 10 URBs active at any given time in this > driver, which does not explain why we get 256 allocations. I think the audio part of the em28xx bridge is not used in my DVB tests. Are there other allocations from orion-ehci directly? Maybe something special for isochronous transfers (since there is no problem with my other dvb sticks using bulk transfers)? > I also noticed that the initial submissions are all atomic but don't > need to, so it may be worth trying the patch below, which should also > help in low-memory situations. We could also try moving the resubmission > into a workqueue in order to let those be GFP_KERNEL, but I don't think > that will help. I built a linux-3.7.4 with the em28xx patch and both of your dma-mapping.c patches. I still see the ERROR: 1024 KiB atomic DMA coherent pool is too small! Soeren -- 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/ . Don't email: email@kvack.org