From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754183Ab0IQNrl (ORCPT ); Fri, 17 Sep 2010 09:47:41 -0400 Received: from mail-wy0-f174.google.com ([74.125.82.174]:59965 "EHLO mail-wy0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752474Ab0IQNrj convert rfc822-to-8bit (ORCPT ); Fri, 17 Sep 2010 09:47:39 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=date:from:to:cc:subject:message-id:in-reply-to:references:x-mailer :mime-version:content-type:content-transfer-encoding; b=Z6CUi7PiKHMfGJNo2CKCq/+U+Qgf26vh+LRhANTsjqMhnnFJyJ33igpY+JmrTBGVgz 2TXVQzZ8atF++a45g3IF8eMyf+DDvCSF9qf/4/crGEXkny6lbjA2KZZZ198yHWd5hZfT OiSUSRwsTvtO5v2RC5ES01nsatAC1e6B1niKg= Date: Fri, 17 Sep 2010 15:47:32 +0200 From: Alejandro Riveira =?UTF-8?B?RmVybsOhbmRleg==?= To: "Joshua Hintze" Cc: , linux-ide@vger.kernel.org Subject: Re: PATA IDE is slower in newer versions of kernel Message-ID: <20100917154732.330c4b1b@varda> In-Reply-To: <00d401cb55f7$33a78210$9af68630$@com> References: <00d401cb55f7$33a78210$9af68630$@com> X-Mailer: Claws Mail 3.7.6 (GTK+ 2.20.1; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 I have recently taken the plunge to update to a newer version of the kernel 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/