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 9ECA52BE5; Thu, 8 Nov 2018 16:59:28 +0100 (CET) Received: from compute1.internal (compute1.nyi.internal [10.202.2.41]) by mailout.nyi.internal (Postfix) with ESMTP id 01162223B5; Thu, 8 Nov 2018 10:59:26 -0500 (EST) Received: from mailfrontend1 ([10.202.2.162]) by compute1.internal (MEProxy); Thu, 08 Nov 2018 10:59:26 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=monjalon.net; h= from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding:content-type; s=mesmtp; bh=Hxh18EXtDEUDLpuVf6kzL0+4xMcYa6VrAeyRbLeDpEg=; b=U3jnAX9WS+a2 t6CI5Oc6bZucekdNQ4nu4Y8L8ZrEp+iEFXadFv1iigeI9pJZFaTjO2gIjhJzazZK iQ5B15KopILbfOdbrXiqu6VZDA7N9AjbdGoeUEdFk69McCqvavo+udbX35lHUtO2 UoN4xjwtWLAGtxkSoBM0g71r2z+ZLHw= 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-proxy:x-me-proxy:x-me-sender:x-me-sender :x-sasl-enc; s=fm1; bh=Hxh18EXtDEUDLpuVf6kzL0+4xMcYa6VrAeyRbLeDp Eg=; b=TnCMbB57ugOsTBFeH5btubVvopbgtjCkJSN3PXo0ly1PrjhDPta0ENVck 1r8LWK1Jg83nQgD1DEMNRFUEgdH2VhFuzlulTuLICjonWbo/aLbzZaG3PCvJxdnp WD8HUwoJ6iPwAmsGocXmOgvTmBYiD1qo2Ug6AgrcVVWKtfdGHk5tKESHkaIab1dM AvW+Bf0KsuZ6qdzIwsE8QVlVerfl3oRfVSeEqQ14n4j5pYpmHWDq9c3UVlnThIuw L89rEsdVbv+YRaLAwAyD8W9kl3RLnb4FLmGUf+R99qN0mLG4N56hQAFx6IZ+K7eN N5vwpJyAjov1YcCMxjJ+iCmMRE4sw== X-ME-Sender: X-ME-Proxy: Received: from xps.localnet (184.203.134.77.rev.sfr.net [77.134.203.184]) by mail.messagingengine.com (Postfix) with ESMTPA id B630BE4939; Thu, 8 Nov 2018 10:59:23 -0500 (EST) From: Thomas Monjalon To: keith.wiles@intel.com, Yongseok Koh , ferruh.yigit@intel.com Cc: dev@dpdk.org, bruce.richardson@intel.com, Shahaf Shuler , konstantin.ananyev@intel.com, anatoly.burakov@intel.com, stable@dpdk.org, justin.parus@microsoft.com, christian.ehrhardt@canonical.com, david.coronel@canonical.com, josh.powers@canonical.com, jay.vosburgh@canonical.com, dan.streetman@canonical.com Date: Thu, 08 Nov 2018 16:59:22 +0100 Message-ID: <1612642.At0RDolh7h@xps> In-Reply-To: <432F92CE-5714-45DC-B72F-CD8771DAFC89@intel.com> References: <20181023212318.43082-1-yskoh@mellanox.com> <432F92CE-5714-45DC-B72F-CD8771DAFC89@intel.com> MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="us-ascii" Subject: Re: [dpdk-dev] AVX512 bug on SkyLake 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, 08 Nov 2018 15:59:28 -0000 Hi, We need to gather more information about this bug. More below. 07/11/2018 10:04, Wiles, Keith: > > On Nov 6, 2018, at 9:30 PM, Yongseok Koh wrote: > >> On Nov 5, 2018, at 6:06 AM, Wiles, Keith wrote: > >>> On Nov 2, 2018, at 9:04 PM, Yongseok Koh wrote: > >>> > >>> This is a workaround to prevent a crash, which might be caused by > >>> optimization of newer gcc (7.3.0) on Intel Skylake. > >> > >> Should the code below not also test for the gcc version and > >> the Sky Lake processor, maybe I am wrong but it seems it is > >> turning AVX512 for all GCC builds > > > > I didn't want to check gcc version as 7.3.0 is very new. Only gcc 8 is newly up since then (gcc 8.2). > > Also, I wasn't able to test every gcc versions and I wanted to be a bit conservative for this crash. > > Performance drop (if any) by disabling a new (experimental) feature would be less risky than unaccountable crash. > > And, it does disable the feature only if CONFIG_RTE_ENABLE_AVX512=n. Please refer to v3. > > Are you not turning off all of the GCC versions for AVX512. > And you can test for range or greater then GCC version and > it just seems like we are turning off every gcc version, is that true? Do we know exactly which GCC versions are affected? > >> Also bug 97 seems a bit obscure reference, maybe you know > >> the bug report, but more details would be good? > > > > I sent out the report to dev list two month ago. > > And I created the Bug 97 in order to reference it > > in the commit message. > > I didn't want to repeat same message here and there, > > but it would've been better to have some sort of summary > > of the Bug, although v3 has a few more words. > > However, v3 has been merged. > > Still this is too obscure if nothing else give a link to > a specific bug not just 97. The URL is https://bugs.dpdk.org/show_bug.cgi?id=97 The bug is also pointing to an email: https://mails.dpdk.org/archives/dev/2018-September/111522.html Summary: - CPU: Intel Skylake - Linux environment: Ubuntu 18.04 - Compiler: gcc-7.3 (Ubuntu 7.3.0-16ubuntu3) - Scenario: testpmd crashes when it starts forwarding - Behaviour: AVX2 version of rte_memcpy() optimized with 512b instructions - Fix: disable AVX512 optimization with -mno-avx512f It seems to have been reproduced only when using mlx5 PMD so far. Any other experience?