From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mga05.intel.com (mga05.intel.com [192.55.52.43]) by dpdk.org (Postfix) with ESMTP id 807D94C99; Fri, 9 Nov 2018 11:03:34 +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 fmsmga105.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 09 Nov 2018 02:03:33 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.54,483,1534834800"; d="scan'208";a="106825952" Received: from fyigit-mobl.ger.corp.intel.com (HELO [10.237.221.79]) ([10.237.221.79]) by orsmga001.jf.intel.com with ESMTP; 09 Nov 2018 02:03:30 -0800 To: Yongseok Koh Cc: Thomas Monjalon , "Wiles, Keith" , dev , "Richardson, Bruce" , 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> <9d3f48fc-5a47-c813-1da8-7e1cab6bdd9e@intel.com> From: Ferruh Yigit Openpgp: preference=signencrypt Autocrypt: addr=ferruh.yigit@intel.com; prefer-encrypt=mutual; keydata= xsFNBFXZCFABEADCujshBOAaqPZpwShdkzkyGpJ15lmxiSr3jVMqOtQS/sB3FYLT0/d3+bvy qbL9YnlbPyRvZfnP3pXiKwkRoR1RJwEo2BOf6hxdzTmLRtGtwWzI9MwrUPj6n/ldiD58VAGQ +iR1I/z9UBUN/ZMksElA2D7Jgg7vZ78iKwNnd+vLBD6I61kVrZ45Vjo3r+pPOByUBXOUlxp9 GWEKKIrJ4eogqkVNSixN16VYK7xR+5OUkBYUO+sE6etSxCr7BahMPKxH+XPlZZjKrxciaWQb +dElz3Ab4Opl+ZT/bK2huX+W+NJBEBVzjTkhjSTjcyRdxvS1gwWRuXqAml/sh+KQjPV1PPHF YK5LcqLkle+OKTCa82OvUb7cr+ALxATIZXQkgmn+zFT8UzSS3aiBBohg3BtbTIWy51jNlYdy ezUZ4UxKSsFuUTPt+JjHQBvF7WKbmNGS3fCid5Iag4tWOfZoqiCNzxApkVugltxoc6rG2TyX CmI2rP0mQ0GOsGXA3+3c1MCdQFzdIn/5tLBZyKy4F54UFo35eOX8/g7OaE+xrgY/4bZjpxC1 1pd66AAtKb3aNXpHvIfkVV6NYloo52H+FUE5ZDPNCGD0/btFGPWmWRmkPybzColTy7fmPaGz cBcEEqHK4T0aY4UJmE7Ylvg255Kz7s6wGZe6IR3N0cKNv++O7QARAQABzSVGZXJydWggWWln aXQgPGZlcnJ1aC55aWdpdEBpbnRlbC5jb20+wsGVBBMBAgA/AhsDBgsJCAcDAgYVCAIJCgsE FgIDAQIeAQIXgBYhBNI2U4dCLsKE45mBx/kz60PfE2EfBQJbughWBQkHwjOGAAoJEPkz60Pf E2Eft84QAIbKWqhgqRfoiw/BbXbA1+qm2o4UgkCRQ0yJgt9QsnbpOmPKydHH0ixCliNz1J8e mRXCkMini1bTpnzp7spOjQGLeAFkNFz6BMq8YF2mVWbGEDE9WgnAxZdi0eLY7ZQnHbE6AxKL SXmpe9INb6z3ztseFt7mqje/W/6DWYIMnH3Yz9KzxujFWDcq8UCAvPkxVQXLTMpauhFgYeEx Nub5HbvhxTfUkapLwRQsSd/HbywzqZ3s/bbYMjj5JO3tgMiM9g9HOjv1G2f1dQjHi5YQiTZl 1eIIqQ3pTic6ROaiZqNmQFXPsoOOFfXF8nN2zg8kl/sSdoXWHhama5hbwwtl1vdaygQYlmdK H2ueiFh/UvT3WG3waNv2eZiEbHV8Rk52Xyn2w1G90lV0fYC6Ket1Xjoch7kjwbx793Kz/RfQ rmBY8/S4DTGn3oq3dMdQY+b6+7VMUeLMMh2CXYO9ErkOq+qNTD1IY+cBAkXnaDbQfz0zbste ZGWH74FAZ9nCpDOqbRTrBL42aMGhfOWEyeA1x7+hl6JZfabBWAuf4nnCXuorKHzBXTrf7u7p fXsKQClWRW77PF1VmzrtKNVSytQAmlCWApQIw20AarFipXmVdIjHmJPU611WoyxZPb4JTOxx 5cv9B+nr/RIB+v5dcStyHCCwO1be7nBDdCgd4F6kTQPLzsFNBFfWTL4BEACnNA29e8TarUsB L5n6eLZHXcFvVwNLVlirWOClHXf44o2KnN3ww+eBEmKVfEFo9MSuGDNHS8Zw1NiGMYxLIUgd U6gGrVVs/VrQWL82pbMk6jCj98N+BXIri+6K1z+AImz7ax7iF1kDgRAnFWU0znWWBgM2mM8Y gDjcxfXk4sCKnvf6Gjo08Ey5zmqx7dekAKU2EEp8Q1EJY3jbymLdZWRP4AFFMTS1rGMk0/tt v71NBg1GobCcbNfn9chK/jhqxYhAJqq86RdJQkt3/9x1U1Oq0vXCt4JVVHmkxePtUiuWTTt+ aYlUAsKYZsWvncExvw77x2ArYDmaK0yfjh37wp0lY7DOJHFxoyT8tyWZlLci/VMRG2Ja33xj 0CN4C1yBg+QDeV3QFxQo42iA/ykdXPUR3ezmsND3XKvVLTC4DNb3V/EZQ7jBj64+bEK0VW4G B31VP00ApNQvSoczsIOAKdk97RNbpmPw6q10ILIB+9T1xbnFYzshzGF17oC0/GENIHATx8vZ masOZoDiOZQpeneLgnFE9JfzhLTxv6wNZcc/HLXRQVTkDsQr8ERtkAoHCf1E5+b5Yr7pfnE4 YuhET746o25S53ELUYPIs49qoJsEJL34/oexMfPGyPIlrbufiNyty5jc/1MRwUlhJlJ5IOHy ZUa+6CLR7GdImusFkPJUJwARAQABwsF8BBgBAgAmAhsMFiEE0jZTh0IuwoTjmYHH+TPrQ98T YR8FAlu6CHAFCQXE7zIACgkQ+TPrQ98TYR9nXxAAqNBgkYNyGuWUuy0GwDQCbu3iiMyH1+D7 llafPcK4NYy1Z4AYuVwC9nmLaoj+ozdqS3ncRo57ncRsKEJC46nDJJZYZ5LSJVn63Y3NBF86 lxQAgjj2oyZEwaLKtKbAFsXL43jv1pUGgSvWwYtDwHITXXFQto9rZEuUDRFSx4sg9OR+Q6/6 LY+nQQ3OdHlBkflzYMPcWgDcvcTAO6yasLEUf7UcYoSWTyMYjLB4QuNlXzTswzGVMssJF/vo V8lD1eqqaSUWG3STF6GVLQOr1NLvN5+kUBiEStHFxBpgSCvYY9sNV8FS6N24CAWMBl+10W+D 2h1yiiP5dOdPcBDYKsgqDD91/sP0WdyMJkwdQJtD49f9f+lYloxHnSAxMleOpyscg1pldw+i mPaUY1bmIknLhhkqfMmjywQOXpac5LRMibAAYkcB8v7y3kwELnt8mhqqZy6LUsqcWygNbH/W K3GGt5tRpeIXeJ25x8gg5EBQ0Jnvp/IbBYQfPLtXH0Myq2QuAhk/1q2yEIbVjS+7iowEZNyE 56K63WBJxsJPB2mvmLgn98GqB4G6GufP1ndS0XDti/2K0o8rep9xoY/JDGi0n0L0tk9BHyoP Y7kaEpu7UyY3nVdRLe5H1/MnFG8hdJ97WqnPS0buYZlrbTV0nRFL/NI2VABl18vEEXvNQiO+ vM8= Message-ID: <9891a520-492a-2d18-65e7-c4fcd96a5e3f@intel.com> Date: Fri, 9 Nov 2018 10:03:29 +0000 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:60.0) Gecko/20100101 Thunderbird/60.3.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit 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: Fri, 09 Nov 2018 10:03:35 -0000 On 11/8/2018 11:01 PM, Yongseok Koh wrote: > >> On Nov 8, 2018, at 9:21 AM, Ferruh Yigit wrote: >> >> 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://emea01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fbugs.dpdk.org%2Fshow_bug.cgi%3Fid%3D97&data=02%7C01%7Cyskoh%40mellanox.com%7C90ff6c361faf422b976108d6459eb490%7Ca652971c7d2e4d9ba6a4d149256f461b%7C0%7C0%7C636772945282345908&sdata=2o%2Fg203aWrKCYg16S6oI4BcS41igpLu1DloS%2FrRnknc%3D&reserved=0 >>> The bug is also pointing to an email: >>> https://emea01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fmails.dpdk.org%2Farchives%2Fdev%2F2018-September%2F111522.html&data=02%7C01%7Cyskoh%40mellanox.com%7C90ff6c361faf422b976108d6459eb490%7Ca652971c7d2e4d9ba6a4d149256f461b%7C0%7C0%7C636772945282345908&sdata=NCFKxaREd69iZ8eyFKg%2FWBP73CLTXkxrNQQeii%2Bbsao%3D&reserved=0 >>> >>> 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? > > Nothing's impossible but even with my quick search in gcc.gnu.org, > I could find the following documents mention mavx512f support: > > GCC 4.9.0 > April 22, 2014 (changes, documentation) > > GCC 5.1 > April 22, 2015 (changes, documentation) > > GCC 6.4 > July 4, 2017 (changes, documentation) > > GCC 7.1 > May 2, 2017 (changes, documentation) > > GCC 8.1 > May 2, 2018 (changes, documentation) > > We altogether have to put quite large resource to verify all of the versions. > > I assumed older than gcc 7 would have the same issue. I know it was a speculation > but like I mentioned I wanted to be more conservative. I didn't mean this is a permanent fix. > For two months, we couldn't have any tangible solution (actually nobody cared including myself), > so I submitted the patch to temporarily disable mavx512f. > > I'm still not sure what the best option is... For permanent fix we need more information, currently we can't re-produce this defect. Since you can reproduce it we need your support. Right now we don't know if this is compiler issue or code defect in rte_memcpy() or something else. It is easy to disable mavx512f as temporarily solution but it is coming with the cost of the performance drop, also without knowing the actual root cause I wouldn't say this is being conservative, actual issue may be just hidden with this change. I think as first thing we need to find a way to reproduce this issue in any other way than using mlx5 PMD. So that we can put more organized effort to fix this. I attached a simple unit test for rte_memcpy(), if this is a rte_memcpy() with avx512f defect as claimed, you should be able to see the issue with that, right? Did you able to find a chance to test it? Do you observer any crash there? > > Thanks, > Yongseok > >> >>> - 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? >