From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mga11.intel.com (mga11.intel.com [192.55.52.93]) by dpdk.org (Postfix) with ESMTP id F25C8493D; Thu, 8 Nov 2018 18:22:03 +0100 (CET) X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga001.jf.intel.com ([10.7.209.18]) by fmsmga102.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 08 Nov 2018 09:22:02 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.54,480,1534834800"; d="scan'208";a="106580103" Received: from fyigit-mobl.ger.corp.intel.com (HELO [10.237.221.79]) ([10.237.221.79]) by orsmga001.jf.intel.com with ESMTP; 08 Nov 2018 09:21:59 -0800 To: Thomas Monjalon , keith.wiles@intel.com, Yongseok Koh 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 References: <20181023212318.43082-1-yskoh@mellanox.com> <432F92CE-5714-45DC-B72F-CD8771DAFC89@intel.com> <1612642.At0RDolh7h@xps> From: Ferruh Yigit Openpgp: preference=signencrypt Autocrypt: addr=ferruh.yigit@intel.com; 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WOW64; rv:60.0) Gecko/20100101 Thunderbird/60.3.0 MIME-Version: 1.0 In-Reply-To: <1612642.At0RDolh7h@xps> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit 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 17:22:04 -0000 On 11/8/2018 3:59 PM, Thomas Monjalon wrote: > 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) Is it possible to test a few other gcc versions to check if the issue is specific to this compiler version? > - 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? > >