From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752654AbaKLKDG (ORCPT ); Wed, 12 Nov 2014 05:03:06 -0500 Received: from michael.mail.tiscali.it ([213.205.33.246]:43206 "EHLO michael.mail.tiscali.it" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751954AbaKLKDC (ORCPT ); Wed, 12 Nov 2014 05:03:02 -0500 X-Greylist: delayed 501 seconds by postgrey-1.27 at vger.kernel.org; Wed, 12 Nov 2014 05:03:02 EST Message-ID: <54632E58.60709@assyoma.it> Date: Wed, 12 Nov 2014 10:54:32 +0100 From: Gionatan Danti Organization: Assyoma s.r.l. User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.7.0 MIME-Version: 1.0 To: linux-kernel@vger.kernel.org CC: g.danti@assyoma.it Subject: Re: AHCI maximum transfer size References: <5417FB30.8030908@assyoma.it> In-Reply-To: <5417FB30.8030908@assyoma.it> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 16/09/2014 10:56, Gionatan Danti wrote: >> Hi all, >> I searched the list and the internet for this question, but I did not >> find a definitive answer. >> >> I wonder what is the maximum AHCI transfer size for kernel 2.6.32.x >> Let me explain: using a command as "dd if=/dev/zero of=/dev/sda bs=2M" I >> can see, via iostat, that request-size is at 2M (as expected). However >> it seems to me that the effective transfer size is way lower: disabling >> writeback cache on the target disk, I see very low performance even for >> big-chunk transfers. >> >> Googling, I found this post on stackoverflow stating that maximum >> observerd AHCI transfer size (with a SATA protocol analyzer) is 128KB: >> http://stackoverflow.com/questions/24053662/how-to-enlarge-sata-transfer-size-in-linux-ahci-driver. >> >> >> The stackoverflow post seems to agree with this old LWN.net article: >> http://lwn.net/Articles/77981/ >> >> Anyone has any idea of how to find (and eventually change) the used AHCI >> transfer size without touching the code? >> >> NOTE: please CC me directly. >> Regards. >> > > Hi all, > any idea on the subject? > > Regards. Hi guys, anyone with a suggestion? Thank you. -- Danti Gionatan Supporto Tecnico Assyoma S.r.l. - www.assyoma.it email: g.danti@assyoma.it - info@assyoma.it GPG public key ID: FF5F32A8