From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mga09.intel.com (mga09.intel.com [134.134.136.24]) by dpdk.org (Postfix) with ESMTP id C96021B122; Tue, 8 Jan 2019 04:50:36 +0100 (CET) X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga002.jf.intel.com ([10.7.209.21]) by orsmga102.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 07 Jan 2019 19:50:35 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.56,452,1539673200"; d="scan'208";a="124205971" Received: from fmsmsx105.amr.corp.intel.com ([10.18.124.203]) by orsmga002.jf.intel.com with ESMTP; 07 Jan 2019 19:50:35 -0800 Received: from fmsmsx101.amr.corp.intel.com (10.18.124.199) by FMSMSX105.amr.corp.intel.com (10.18.124.203) with Microsoft SMTP Server (TLS) id 14.3.408.0; Mon, 7 Jan 2019 19:50:34 -0800 Received: from bgsmsx155.gar.corp.intel.com (10.224.48.102) by fmsmsx101.amr.corp.intel.com (10.18.124.199) with Microsoft SMTP Server (TLS) id 14.3.408.0; Mon, 7 Jan 2019 19:50:33 -0800 Received: from bgsmsx101.gar.corp.intel.com ([169.254.1.147]) by BGSMSX155.gar.corp.intel.com ([169.254.12.54]) with mapi id 14.03.0415.000; Tue, 8 Jan 2019 09:20:31 +0530 From: "Varghese, Vipin" To: "Yigit, Ferruh" , Thomas Monjalon , "Mcnamara, John" , "Kovacevic, Marko" CC: "dev@dpdk.org" , "stable@dpdk.org" , "Tom Barbette" , Yongseok Koh , "Ananyev, Konstantin" , "Richardson, Bruce" Thread-Topic: [PATCH v4] mk: fix scope of disabling AVX512F support Thread-Index: AQHUpqkLGcoiCOECuUav7dZCJuUywKWkvLTw Date: Tue, 8 Jan 2019 03:50:30 +0000 Message-ID: <4C9E0AB70F954A408CC4ADDBF0F8FA7D4D2E11A8@BGSMSX101.gar.corp.intel.com> References: <20190103162313.85623-1-ferruh.yigit@intel.com> <20190107164942.88785-1-ferruh.yigit@intel.com> In-Reply-To: <20190107164942.88785-1-ferruh.yigit@intel.com> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-originating-ip: [10.223.10.10] Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 Subject: Re: [dpdk-stable] [PATCH v4] mk: fix scope of disabling AVX512F support X-BeenThere: stable@dpdk.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: patches for DPDK stable branches List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 08 Jan 2019 03:50:37 -0000 =20 diff --git a/doc/guides/rel_notes/known_issues.rst b/doc/guides/rel_notes/k= nown_issues.rst index a1face9c1..b0057a2bc 100644 --- a/doc/guides/rel_notes/known_issues.rst +++ b/doc/guides/rel_notes/known_issues.rst @@ -826,3 +826,35 @@ Kernel crash when hot-unplug igb_uio device while DPDK= application is running =20 **Driver/Module**: ``igb_uio`` module. + + +AVX-512 support disabled +------------------------ + +**Description**: + ``AVX-512`` support has been disabled on some conditions. + This shouldn't be confused with ``CONFIG_RTE_ENABLE_AVX512`` config opt= ion which is already + disabled by default. This config option defines if ``AVX-512`` specific= implementations of + some file to be used or not. What has been disabled is compiler feature= to produce ``AVX-512`` + instructions from any source code. + + On DPDK v18.11 ``AVX-512`` disabled for all ``GCC`` builds which report= ed to cause a performance + drop. + + On DPDK v19.02 ``AVX-512`` disable scope reduced to ``GCC`` and ``binut= ils version 2.30`` based + on information accured from the GCC community defect. + +**Reason**: + Generated ``AVX-512`` code cause crash: + https://bugs.dpdk.org/show_bug.cgi?id=3D97 + https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D88096 + +**Resolution/Workaround**: + Update ``binutils`` to newer version than ``2.30``. + Use different compiler, like ``clang`` for this case. + +**Affected Environment/Platform**: + ``GCC`` and ``binutils version 2.30``. + +**Driver/Module**: + ALL. diff --git a/doc/guides/rel_notes/release_19_02.rst b/doc/guides/rel_notes/= release_19_02.rst index 39c6ff826..b6322b282 100644 --- a/doc/guides/rel_notes/release_19_02.rst +++ b/doc/guides/rel_notes/release_19_02.rst @@ -276,6 +276,19 @@ Known Issues Also, make sure to start the actual text at the margin. =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D =20 +* ``AVX-512`` support has been disabled for ``GCC`` builds when=20 +``binutils 2.30`` + is detected [1] because of a crash [2]. This can affect ``native``=20 +machine type + build targets on the platforms that support ``AVX512F`` like ``Intel=20 +Skylake`` + processors, and can cause a possible performance drop. The immediate=20 +workaround + is to use ``clang`` compiler on these platforms. + Initial workaround in DPDK v18.11 was to disable ``AVX-512`` support=20 +for ``GCC`` + completely, but based on information on defect submitted to GCC=20 +community [3], + issue has been identified as ``binutils 2.30`` issue. Since currently=20 +only GCC + generates ``AVX-512`` instructions, scope limited to ``GCC`` and=20 +``binutils 2.30`` + + - [1]: Commit ("mk: fix scope of disabling AVX512F support") + - [2]: https://bugs.dpdk.org/show_bug.cgi?id=3D97 + - [3]: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D88096 =20 Sharing ACK for documentation and update in release notes Acked-by: Vipin Varghese