From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: <thomas@monjalon.net> Received: from out4-smtp.messagingengine.com (out4-smtp.messagingengine.com [66.111.4.28]) by dpdk.org (Postfix) with ESMTP id 84C0C1B7E0 for <dev@dpdk.org>; Wed, 25 Oct 2017 09:25:23 +0200 (CEST) Received: from compute1.internal (compute1.nyi.internal [10.202.2.41]) by mailout.nyi.internal (Postfix) with ESMTP id BBF6A22342; Wed, 25 Oct 2017 03:25:22 -0400 (EDT) Received: from frontend2 ([10.202.2.161]) by compute1.internal (MEProxy); Wed, 25 Oct 2017 03:25:22 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=monjalon.net; h= cc:content-transfer-encoding:content-type:date:from:in-reply-to :message-id:mime-version:references:subject:to:x-me-sender :x-me-sender:x-sasl-enc; s=mesmtp; bh=26tsCwcaDLRoaWSYGZUOWVDdJW jdxSct/rGMTTSNLlk=; b=Dag/Lah/bMHId1xFjfa68wrZ4m8ExIrm8WUGU7ZNj2 O8PwLMO1Jmo4WkiluYlKOpiSK3HvE4P/KQh4tBs/lI7TZbvdjOC99PIz+UnfMHO7 d+85LrKq6gf44M8CU8zyRtZaM7AH8XTKb7f8ioQhI8UM/IcdamoYpneKf/i3HwVD 4= DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d= messagingengine.com; h=cc:content-transfer-encoding:content-type :date:from:in-reply-to:message-id:mime-version:references :subject:to:x-me-sender:x-me-sender:x-sasl-enc; s=fm1; bh=26tsCw caDLRoaWSYGZUOWVDdJWjdxSct/rGMTTSNLlk=; b=ND+ApmPg8qqLaBAKOSqmkz oEv5d29vfqp3Xl7hFmZfjtvTk15KNtHCSTTTs/bz/SsjoAgkmUkRqQxgjmj25Han /FGtNk0rHqexv16qjcg3i2j+alC3bDMhmw5OAoBPd59axr1KVcsehSjnZsvKmnf7 c8ZQjdgSdHp3jhpYK/QiEIrPNIGGLnn78PJsFMa26Lw5qyjI508jJ5j/sd1U5o3L bhJozdn/rUtx0pJT4jaF1aPjCTNSDg36CF87j6q+yAY+arbRKx0txKl8swtuXYyT Bo9XjuhE0ijhJO91M0n/GywkkmHDwLJR0mJIF+GcXE6k48mlGOFmS7bhBSgzzWFw == X-ME-Sender: <xms:YjzwWbPU9miVW-7zdgPS22CdZpLSYXAfJN3h2AX47J6-q2fYuw3zpg> Received: from xps.localnet (184.203.134.77.rev.sfr.net [77.134.203.184]) by mail.messagingengine.com (Postfix) with ESMTPA id 5C4D424009; Wed, 25 Oct 2017 03:25:22 -0400 (EDT) From: Thomas Monjalon <thomas@monjalon.net> To: "Li, Xiaoyun" <xiaoyun.li@intel.com>, "Richardson, Bruce" <bruce.richardson@intel.com> Cc: dev@dpdk.org, "Ananyev, Konstantin" <konstantin.ananyev@intel.com>, "Lu, Wenzhuo" <wenzhuo.lu@intel.com>, "Zhang, Helin" <helin.zhang@intel.com>, "ophirmu@mellanox.com" <ophirmu@mellanox.com> Date: Wed, 25 Oct 2017 09:25:21 +0200 Message-ID: <8258746.M4EytlN248@xps> In-Reply-To: <B9E724F4CB7543449049E7AE7669D82F4816C5@SHSMSX101.ccr.corp.intel.com> References: <1507206794-79941-1-git-send-email-xiaoyun.li@intel.com> <B9E724F4CB7543449049E7AE7669D82F4801D1@SHSMSX101.ccr.corp.intel.com> <B9E724F4CB7543449049E7AE7669D82F4816C5@SHSMSX101.ccr.corp.intel.com> MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="us-ascii" Subject: Re: [dpdk-dev] [PATCH v8 1/3] eal/x86: run-time dispatch over memcpy X-BeenThere: dev@dpdk.org X-Mailman-Version: 2.1.15 Precedence: list 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, 25 Oct 2017 07:25:23 -0000 25/10/2017 08:55, Li, Xiaoyun: > From: Li, Xiaoyun > > From: Richardson, Bruce > > > On Thu, Oct 19, 2017 at 11:00:33AM +0200, Thomas Monjalon wrote: > > > > 19/10/2017 10:50, Li, Xiaoyun: > > > > > From: Thomas Monjalon > > > > > > 19/10/2017 09:51, Li, Xiaoyun: > > > > > > > From: Thomas Monjalon [mailto:thomas@monjalon.net] > > > > > > > > 19/10/2017 04:45, Li, Xiaoyun: > > > > > > > > > Hi > > > > > > > > > > > > > > > > > > > > > > > > The significant change of this patch is to call a > > > > > > > > > > > > function pointer for packet size > 128 > > > (RTE_X86_MEMCPY_THRESH). > > > > > > > > > > > The perf drop is due to function call replacing inline. > > > > > > > > > > > > > > > > > > > > > > > Please could you provide some benchmark numbers? > > > > > > > > > > > I ran memcpy_perf_test which would show the time cost > > > > > > > > > > > of memcpy. I ran it on broadwell with sse and avx2. > > > > > > > > > > > But I just draw pictures and looked at the trend not > > > > > > > > > > > computed the exact percentage. Sorry about that. > > > > > > > > > > > The picture shows results of copy size of 2, 4, 6, 8, > > > > > > > > > > > 9, 12, 16, 32, 64, 128, 192, 256, 320, 384, 448, 512, > > > > > > > > > > > 768, 1024, 1518, 1522, 1536, 1600, 2048, 2560, 3072, > > > > > > > > > > > 3584, 4096, 4608, 5120, 5632, 6144, 6656, 7168, > > > > > > > > > > 7680, 8192. > > > > > > > > > > > In my test, the size grows, the drop degrades. (Using > > > > > > > > > > > copy time indicates the > > > > > > > > > > > perf.) From the trend picture, when the size is > > > > > > > > > > > smaller than > > > > > > > > > > > 128 bytes, the perf drops a lot, almost 50%. And above > > > > > > > > > > > 128 bytes, it approaches the original dpdk. > > > > > > > > > > > I computed it right now, it shows that when greater > > > > > > > > > > > than > > > > > > > > > > > 128 bytes and smaller than 1024 bytes, the perf drops > > > > > > > > > > > about > > > 15%. > > > > > > > > > > > When above > > > > > > > > > > > 1024 bytes, the perf drops about 4%. > > > > > > > > > > > > > > > > > > > > > > > From a test done at Mellanox, there might be a > > > > > > > > > > > > performance degradation of about 15% in testpmd > > > > > > > > > > > > txonly > > > with AVX2. > > > > > > > > > > > > > > > > > > > > > > > > > > > > I did tests on X710, XXV710, X540 and MT27710 but didn't > > > > > > > > > see > > > > > > > > performance degradation. > > > > > > > > > > > > > > > > > > I used command "./x86_64-native-linuxapp-gcc/app/testpmd > > > > > > > > > -c 0xf -n > > > > > > > > > 4 -- - > > > > > > > > I" and set fwd txonly. > > > > > > > > > I tested it on v17.11-rc1, then revert my patch and tested it > > again. > > > > > > > > > Show port stats all and see the throughput pps. But the > > > > > > > > > results are similar > > > > > > > > and no drop. > > > > > > > > > > > > > > > > > > Did I miss something? > > > > > > > > > > > > > > > > I do not understand. Yesterday you confirmed a 15% drop with > > > > > > > > buffers between > > > > > > > > 128 and 1024 bytes. > > > > > > > > But you do not see this drop in your txonly tests, right? > > > > > > > > > > > > > > > Yes. The drop is using test. > > > > > > > Using command "make test -j" and then " ./build/app/test -c f -n 4 " > > > > > > > Then run "memcpy_perf_autotest" > > > > > > > The results are the cycles that memory copy costs. > > > > > > > But I just use it to show the trend because I heard that it's > > > > > > > not > > > > > > recommended to use micro benchmarks like test_memcpy_perf for > > > > > > memcpy performance report as they aren't likely able to reflect > > > > > > performance of real world applications. > > > > > > > > > > > > Yes real applications can hide the memcpy cost. > > > > > > Sometimes, the cost appear for real :) > > > > > > > > > > > > > Details can be seen at > > > > > > > https://software.intel.com/en-us/articles/performance-optimiza > > > > > > > ti > > > > > > > on-of- > > > > > > > memcpy-in-dpdk > > > > > > > > > > > > > > And I didn't see drop in testpmd txonly test. Maybe it's > > > > > > > because not a lot > > > > > > memcpy calls. > > > > > > > > > > > > It has been seen in a mlx4 use-case using more memcpy. > > > > > > I think 15% in micro-benchmark is too much. > > > > > > What can we do? Raise the threshold? > > > > > > > > > > > I think so. If there is big drop, can try raise the threshold. Maybe 1024? > > > but not sure. > > > > > But I didn't reproduce the 15% drop on mellanox and not sure how > > > > > to > > > verify it. > > > > > > > > I think we should focus on micro-benchmark and find a reasonnable > > > > threshold for a reasonnable drop tradeoff. > > > > > > > Sadly, it may not be that simple. What shows best performance for > > > micro- benchmarks may not show the same effect in a real application. > > > > > > /Bruce > > > > Then how to measure the performance? > > > > And I cannot reproduce 15% drop on mellanox. > > Could the person who tested 15% drop help to do test again with 1024 > > threshold and see if there is any improvement? > > As Bruce said, best performance on micro-benchmark may not show the same effect in real applications. Yes real applications may hide the impact. You keep saying that it is a reason to allow degrading memcpy raw perf. But can you see better performance with buffers of 256 bytes with any application thanks to your patch? I am not sure whether there is a benefit keeping a code which imply a signicative drop in micro-benchmarks. > And I cannot reproduce the 15% drop. > And I don't know if raising the threshold can improve the perf or not. > Could the person who tested 15% drop help to do test again with 1024 threshold and see if there is any improvement? We will test a increased threshold today.