From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from out4-smtp.messagingengine.com (out4-smtp.messagingengine.com [66.111.4.28]) by dpdk.org (Postfix) with ESMTP id 521351AF03 for ; Thu, 19 Oct 2017 11:00:35 +0200 (CEST) Received: from compute1.internal (compute1.nyi.internal [10.202.2.41]) by mailout.nyi.internal (Postfix) with ESMTP id C6C4020840; Thu, 19 Oct 2017 05:00:34 -0400 (EDT) Received: from frontend2 ([10.202.2.161]) by compute1.internal (MEProxy); Thu, 19 Oct 2017 05:00:34 -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=/vnCbeXCVr2YeADrFxFZMiu66i SLv78fUKeoT8WM6FM=; b=sLsJd8xcV/DbQl78gBfrBitbKxSMM2g7GHGKSGvMTJ 3EpNHnsxppQDhcXbP9ZWXpBzco2JiDwyrwdU3z1ZdDTppcx71YYIC4lboUicnWhE T3WjQbzm3PtN10b+RaQKvhQst2JIGGl/o05aX/v6KZnrfvzymFbbRo0MwoibadHd w= 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=/vnCbe XCVr2YeADrFxFZMiu66iSLv78fUKeoT8WM6FM=; b=q5dmt1jtqj3SNlipHz9l/L 5ORiL8N/H/935zBwvt2lEM2K+D3DUDlA1mjGbMFX5kgQGj7Ix9VCYLw2x0W5Eud1 wQ80mEfxY3zbs4Se3bhKXXNOcHvO7E6bzAuYjMsw2/jARc73BB1rPFk23x/P6VLm TlYgIrkNyr/ImLoLJYro3d3Iv3qxuVzVe/7wWC//ZscmrLDShbzmyTB0lXRe1Ty/ YgijDX7ykZwpOeETZjnpFUkBljrSkffla1ziufOju9X1LIb25tGUcNsKsWAayFXz OUflGY832EhF/Uz6gPZgoCl2xB+3EDMuxpKbxlIwveA5N9YgqNAnj5plP6bLV/Mw == X-ME-Sender: Received: from xps.localnet (184.203.134.77.rev.sfr.net [77.134.203.184]) by mail.messagingengine.com (Postfix) with ESMTPA id 68FB124347; Thu, 19 Oct 2017 05:00:34 -0400 (EDT) From: Thomas Monjalon To: "Li, Xiaoyun" Cc: "Ananyev, Konstantin" , "Richardson, Bruce" , dev@dpdk.org, "Lu, Wenzhuo" , "Zhang, Helin" , "ophirmu@mellanox.com" Date: Thu, 19 Oct 2017 11:00:33 +0200 Message-ID: <4686516.j2scn2ENsX@xps> In-Reply-To: References: <1507206794-79941-1-git-send-email-xiaoyun.li@intel.com> <3438028.jIYWTcBuhA@xps> 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 List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 19 Oct 2017 09:00:35 -0000 19/10/2017 10:50, Li, Xiaoyun: > > > -----Original Message----- > > From: Thomas Monjalon [mailto:thomas@monjalon.net] > > Sent: Thursday, October 19, 2017 16:34 > > To: Li, Xiaoyun > > Cc: Ananyev, Konstantin ; Richardson, > > Bruce ; dev@dpdk.org; Lu, Wenzhuo > > ; Zhang, Helin ; > > ophirmu@mellanox.com > > Subject: Re: [dpdk-dev] [PATCH v8 1/3] eal/x86: run-time dispatch over > > memcpy > > > > 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-optimization-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.