From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from smtp.codeaurora.org ([198.145.29.96]:46516 "EHLO smtp.codeaurora.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751101AbbKJAnN (ORCPT ); Mon, 9 Nov 2015 19:43:13 -0500 Subject: Re: ECRC and Max Read Request Size To: Bjorn Helgaas References: <56310B34.6000102@codeaurora.org> <20151106172205.GA1002@localhost> <563CE93F.5060209@codeaurora.org> <20151109191517.GA4789@localhost> Cc: linux-pci@vger.kernel.org From: Sinan Kaya Message-ID: <56413D9F.5050902@codeaurora.org> Date: Mon, 9 Nov 2015 19:43:11 -0500 MIME-Version: 1.0 In-Reply-To: <20151109191517.GA4789@localhost> Content-Type: text/plain; charset=windows-1252; format=flowed Sender: linux-pci-owner@vger.kernel.org List-ID: On 11/9/2015 2:15 PM, Bjorn Helgaas wrote: >> I talked to our performance team. They are saying that max read >> >request does not gain you much compared to max payload size single >> >direction but it helps tremendously if you are moving data forth and >> >back between the card. I don't have real numbers though. > I'm not enough of a hardware or performance person to visualize how > MRRS makes a tremendous difference in this situation. Sample > timelines comparing small vs. large MRRS would help everybody > understand what's happening here. > > Bjorn The LSI SAS 9211i card supports 4k maximum read request size. I manually forced this to 4k instead of the maximum payload size of the platform on both the host bridge and the endpoint. I did a quick test with: dd if=/dev/zero of=/dev/sda bs=1G count=1 It gave me %9 higher write performance. -- Sinan Kaya Qualcomm Technologies, Inc. on behalf of Qualcomm Innovation Center, Inc. Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a Linux Foundation Collaborative Project