From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx1.redhat.com (mx1.redhat.com [209.132.183.28]) by dpdk.org (Postfix) with ESMTP id 4C1DC7CB6 for ; Wed, 13 Sep 2017 14:28:45 +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 701955D689; Wed, 13 Sep 2017 12:28:44 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mx1.redhat.com 701955D689 Authentication-Results: ext-mx10.extmail.prod.ext.phx2.redhat.com; dmarc=none (p=none dis=none) header.from=redhat.com Authentication-Results: ext-mx10.extmail.prod.ext.phx2.redhat.com; spf=fail smtp.mailfrom=aconole@redhat.com Received: from dhcp-25-97.bos.redhat.com (unknown [10.18.25.172]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 672136062A; Wed, 13 Sep 2017 12:28:43 +0000 (UTC) From: Aaron Conole To: Thomas Monjalon Cc: Eelco Chaudron , dev@dpdk.org, jingjing.wu@intel.com, john.mcnamara@intel.com References: <22990026376b08418cb0eb6f028840c03e89f47f.1505221429.git.echaudro@redhat.com> <1863612.973jloI4LL@xps> <65446528.e11mYSnacx@xps> Date: Wed, 13 Sep 2017 08:28:42 -0400 In-Reply-To: <65446528.e11mYSnacx@xps> (Thomas Monjalon's message of "Wed, 13 Sep 2017 00:13:55 +0200") Message-ID: User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/26.0.50 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain 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 [10.5.110.39]); Wed, 13 Sep 2017 12:28:44 +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 List-Id: DPDK patches and discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 13 Sep 2017 12:28:45 -0000 Thomas Monjalon writes: > 12/09/2017 22:29, Aaron Conole: >> Thomas Monjalon writes: >> >> > 12/09/2017 16:50, Aaron Conole: >> >> Eelco Chaudron 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 >> >> >> >> Acked-by: Aaron Conole >> > >> > 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. Ahh, okay. Yep, I agree with all you've written above.