From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from mailout1.w1.samsung.com ([210.118.77.11]:39976 "EHLO mailout1.w1.samsung.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751054Ab3AHGuv (ORCPT ); Tue, 8 Jan 2013 01:50:51 -0500 Message-id: <50EBC1C1.3060208@samsung.com> Date: Tue, 08 Jan 2013 07:50:41 +0100 From: Marek Szyprowski MIME-version: 1.0 To: Mauro Carvalho Chehab Cc: Jonathan Corbet , Alessandro Rubini , federico.vaga@gmail.com, mchehab@infradead.org, pawel@osciak.com, hans.verkuil@cisco.com, giancarlo.asnaghi@st.com, linux-media@vger.kernel.org, linux-kernel@vger.kernel.org, s.nawrocki@samsung.com Subject: Re: [PATCH v3 2/4] videobuf2-dma-streaming: new videobuf2 memory allocator References: <3892735.vLSnhhCRFi@harkonnen> <1348484332-8106-1-git-send-email-federico.vaga@gmail.com> <1399400.izKZgEHXnP@harkonnen> <12929800.xFTBAueAE0@harkonnen> <20130106230947.GA17979@mail.gnudd.com> <20130107124050.3fc5031b@lwn.net> <20130107181500.24c56803@redhat.com> In-reply-to: <20130107181500.24c56803@redhat.com> Content-type: text/plain; charset=UTF-8; format=flowed Content-transfer-encoding: 7bit Sender: linux-media-owner@vger.kernel.org List-ID: On 1/7/2013 9:15 PM, Mauro Carvalho Chehab wrote: > Em Mon, 7 Jan 2013 12:40:50 -0700 > Jonathan Corbet escreveu: > > > On Mon, 7 Jan 2013 00:09:47 +0100 > > Alessandro Rubini wrote: > > > > > I don't expect you'll see serious performance differences on the PC. I > > > think ARM users will have better benefits, due to the different cache > > > architecture. You told me Jon measured meaningful figures on a Marvel > > > CPU. > > > > It made the difference between 10 frames per second with the CPU running > > flat out and 30fps mostly idle. I think that probably counts as > > meaningful, yeah...:) > > Couldn't this performance difference be due to the usage of GFP_DMA inside > the VB2 code, like Federico's new patch series is proposing? > > If not, why are there a so large performance penalty? Nope, this was caused rather by a very poor CPU access to non-cached (aka 'coherent') memory and the way the video data has been accessed/read with CPU. Best regards -- Marek Szyprowski Samsung Poland R&D Center