From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755319Ab0IRRMm (ORCPT ); Sat, 18 Sep 2010 13:12:42 -0400 Received: from mail-da-3.dns-solutions.net ([69.12.112.3]:63528 "HELO mail-da-3.dns-solutions.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1754403Ab0IRRMk convert rfc822-to-8bit (ORCPT ); Sat, 18 Sep 2010 13:12:40 -0400 From: "Joshua Hintze" To: , References: <00d401cb55f7$33a78210$9af68630$@com> <20100917154732.330c4b1b@varda> In-Reply-To: <20100917154732.330c4b1b@varda> Subject: RE: PATA IDE is slower in newer versions of kernel Date: Sat, 18 Sep 2010 11:12:31 -0600 Message-ID: <010901cb5754$ae6735a0$0b35a0e0$@com> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 8BIT X-Mailer: Microsoft Office Outlook 12.0 Thread-Index: ActWbuWuOyhi0fJbQj6BXHxnjBOMQAA5N4rQ Content-Language: en-us Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Some updated information. I created a screen capture of what I am seeing. First is the logic analyzer when the newer linux kernel is writing slow to the PATA port. http://i56.tinypic.com/oqhrug.png Notice in the above link how there is a lot of activating and then large gaps of no activity. After about 9 mS the STOP line is strobed a few times and then DMARQ finally returns to normal operating. The link below shows the picture of an old 2.6.10 kernel where write speeds are much faster. http://i51.tinypic.com/a9wiur.png In the above image notice how the wait time is considerable less 100's of microseconds before the stop lines get strobed. I'm dedicated to continue working on the problem, I just need to advice from the linux community. I've tried different I/O schedulers such as noop and anticipatory and I'm studying the ide-dma code but still lost to where this is happening. Thanks! -----Original Message----- From: linux-ide-owner@vger.kernel.org [mailto:linux-ide-owner@vger.kernel.org] On Behalf Of Alejandro Riveira Fernández Sent: Friday, September 17, 2010 7:48 AM To: Joshua Hintze Cc: linux-kernel@vger.kernel.org; linux-ide@vger.kernel.org Subject: Re: PATA IDE is slower in newer versions of kernel El Thu, 16 Sep 2010 17:30:51 -0600 "Joshua Hintze" escribió: [ Just CC linux-ide ] > Hello, > > I've been digging into this for a couple weeks now. I have an embedded board > that runs Linux Kernel 2.6.10 that is connected to a SSD over a PATA > connection. Data is transferred using UDMA4 speeds and I get a nice > sustained write speed of about 20 MBps which is adequate for us. > > I have recently taken the plunge to update to a newer version of the kernel > starting at 2.6.32 (also tried 2.6.33) and what I am seeing writes speeds > drop to about 18 MBps peak with large jumps going from 8 MBps->16 MBs for > sustained throughput. > > I decided to read up on the ATA specification and I connected a logic > analyzer to the PATA bus and here is what is happening...after a large chunk > of data is written to the device, instead of the device pausing the transfer > by asserting DDMARDY it actual initiates a device data-out termination by > pulling DMARQ low. > > The old kernel 2.6.10 responds to this by strobing the STOP line 8 times > within 800uS and the device releases DMARQ shortly afterwards. On the newer > kernels the strobing of the STOP line takes near 8mS of time. Since the hard > drive only release DMARQ after this 8 pulse strobe I believe this is the > cause of the slower write speeds on the newer kernels. This whole process > happens thousands of times when writing megs of data. So those extra 7mS > begin to add up fast. > > My problem is I've been digging through the ide.c/ide-dma.c and other code > but I'm not exactly sure where the code would jump to upon a device > initiated termination on a data-out dma transfer. > > My guess is ide_dma_intr(...). Is this correct? > > Any other areas I could look at? > > Thanks in advance. > > > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ -- To unsubscribe from this list: send the line "unsubscribe linux-ide" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html No virus found in this incoming message. Checked by AVG - www.avg.com Version: 9.0.851 / Virus Database: 271.1.1/3132 - Release Date: 09/16/10 12:34:00