From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: <echaudro@redhat.com> Received: from mx1.redhat.com (mx1.redhat.com [209.132.183.28]) by dpdk.org (Postfix) with ESMTP id BC8D87CFD for <dev@dpdk.org>; Wed, 13 Sep 2017 10:55:15 +0200 (CEST) Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id C1F1A4E047; Wed, 13 Sep 2017 08:55:14 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mx1.redhat.com C1F1A4E047 Authentication-Results: ext-mx09.extmail.prod.ext.phx2.redhat.com; dmarc=none (p=none dis=none) header.from=redhat.com Authentication-Results: ext-mx09.extmail.prod.ext.phx2.redhat.com; spf=fail smtp.mailfrom=echaudro@redhat.com Received: from rhvm.imac (ovpn-116-204.ams2.redhat.com [10.36.116.204]) by smtp.corp.redhat.com (Postfix) with ESMTP id 88BF76062A; Wed, 13 Sep 2017 08:55:13 +0000 (UTC) To: Thomas Monjalon <thomas@monjalon.net>, Aaron Conole <aconole@redhat.com> Cc: dev@dpdk.org, jingjing.wu@intel.com, john.mcnamara@intel.com References: <22990026376b08418cb0eb6f028840c03e89f47f.1505221429.git.echaudro@redhat.com> <1863612.973jloI4LL@xps> <f7tfubry82w.fsf@dhcp-25-97.bos.redhat.com> <65446528.e11mYSnacx@xps> From: Eelco Chaudron <echaudro@redhat.com> Organization: Red Hat Message-ID: <1a97a98b-98d1-7b0e-37b7-3976b0f2ad93@redhat.com> Date: Wed, 13 Sep 2017 10:55:23 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.3.0 MIME-Version: 1.0 In-Reply-To: <65446528.e11mYSnacx@xps> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Content-Language: en-US X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.38]); Wed, 13 Sep 2017 08:55:15 +0000 (UTC) Subject: Re: [dpdk-dev] [PATCH] app/testpmd: adds mlockall() to fix pages X-BeenThere: dev@dpdk.org X-Mailman-Version: 2.1.15 Precedence: list Reply-To: echaudro@redhat.com List-Id: DPDK patches and discussions <dev.dpdk.org> List-Unsubscribe: <http://dpdk.org/ml/options/dev>, <mailto:dev-request@dpdk.org?subject=unsubscribe> List-Archive: <http://dpdk.org/ml/archives/dev/> List-Post: <mailto:dev@dpdk.org> List-Help: <mailto:dev-request@dpdk.org?subject=help> List-Subscribe: <http://dpdk.org/ml/listinfo/dev>, <mailto:dev-request@dpdk.org?subject=subscribe> X-List-Received-Date: Wed, 13 Sep 2017 08:55:16 -0000 On 13/09/17 00:13, Thomas Monjalon wrote: > 12/09/2017 22:29, Aaron Conole: >> Thomas Monjalon <thomas@monjalon.net> writes: >> >>> 12/09/2017 16:50, Aaron Conole: >>>> Eelco Chaudron <echaudro@redhat.com> writes: >>>> >>>>> Call the mlockall() function, to attempt to lock all of its process >>>>> memory into physical RAM, and preventing the kernel from paging any >>>>> of its memory to disk. >>>>> >>>>> When using testpmd for performance testing, depending on the code path >>>>> taken, we see a couple of page faults in a row. These faults effect >>>>> the overall drop-rate of testpmd. On Linux the mlockall() call will >>>>> prefault all the pages of testpmd (and the DPDK libraries if linked >>>>> dynamically), even without LD_BIND_NOW. >>>>> >>>>> Signed-off-by: Eelco Chaudron <echaudro@redhat.com> >>>> Acked-by: Aaron Conole <aconole@redhat.com> >>> It is interesting, but why make it in testpmd? >>> >>> Maybe it should be documented in this guide: >>> http://dpdk.org/doc/guides/linux_gsg/nic_perf_intel_platform.html >> Well, I'm not sure what the user would be able to do to get the >> prefaulting performance without having a library they use with >> LD_PRELOAD and a function with the constructor attribute which does the >> same thing, AND export LD_BIND_NOW before linking starts. >> >> The LD_BIND_NOW simply does the symbol resolution, but there's no >> guarantee that it will fault all the code pages in to process space, and >> without an mlockall(), I'm not sure that there's any kind of guarantee >> that they don't get swapped out of resident memory (which also leads to >> later page faults). >> >> Maybe I misunderstood the question? > Maybe you misunderstood :) > > I was saying that if this improvement applies to applications, > it should be documented in the tuning guide. > I'll try to find a good place in the documentation for adding a reference to mlockall(), but will send it as a separate documentation patch. //Eelco