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[ { "id": 97818, "web_url": "http://patches.dpdk.org/comment/97818/", "msgid": "<20190630132958.6d2250da@hermes.lan>", "list_archive_url": "https://inbox.dpdk.org/dev/20190630132958.6d2250da@hermes.lan", "date": "2019-06-30T20:29:58", "subject": "Re: [dpdk-dev] [RFC 0/5] use WFE for locks and ring on aarch64", "submitter": { "id": 27, "url": "http://patches.dpdk.org/api/people/27/?format=api", "name": "Stephen Hemminger", "email": "stephen@networkplumber.org" }, "content": "On Mon, 1 Jul 2019 00:21:11 +0800\nGavin Hu <gavin.hu@arm.com> wrote:\n\n> DPDK has multiple use cases where the core repeatedly polls a location in\n> memory. This polling results in many cache and memory transactions.\n> \n> Arm architecture provides WFE (Wait For Event) instruction, which allows\n> the cpu core to enter a low power state until woken up by the update to the\n> memory location being polled. Thus reducing the cache and memory\n> transactions.\n> \n> x86 has the PAUSE hint instruction to reduce such overhead.\n> \n> The rte_wait_until_equal_xxx APIs abstract the functionality of 'polling\n> for a memory location to become equal to a given value'.\n> \n> For non-Arm platforms, these APIs are just wrappers around do-while loop\n> with rte_pause, so there are no performance differences.\n> \n> For Arm platforms, use of WFE can be configured using CONFIG_RTE_USE_WFE\n> option. It is disabled by default.\n> \n> Currently, use of WFE is supported only for aarch64 platforms. armv7\n> platforms do support the WFE instruction, but they require explicit wake up\n> events(sev) and are less performannt.\n> \n> Testing shows that, performance varies across different platforms, with\n> some showing degradation.\n> \n> CONFIG_RTE_USE_WFE should be enabled depending on the performance on the\n> target platforms.\n\nHow does this work if process is preempted?", "headers": { "Return-Path": "<dev-bounces@dpdk.org>", "X-Original-To": "patchwork@dpdk.org", "Delivered-To": "patchwork@dpdk.org", "Received": [ "from [92.243.14.124] (localhost [127.0.0.1])\n\tby dpdk.org (Postfix) with ESMTP id BA7F61B964;\n\tSun, 30 Jun 2019 22:30:10 +0200 (CEST)", "from mail-pl1-f194.google.com (mail-pl1-f194.google.com\n\t[209.85.214.194]) by dpdk.org (Postfix) with ESMTP id A3B4C5424\n\tfor <dev@dpdk.org>; Sun, 30 Jun 2019 22:30:08 +0200 (CEST)", "by mail-pl1-f194.google.com with SMTP id a93so6182510pla.7\n\tfor <dev@dpdk.org>; Sun, 30 Jun 2019 13:30:08 -0700 (PDT)", "from hermes.lan (204-195-22-127.wavecable.com. [204.195.22.127])\n\tby smtp.gmail.com with ESMTPSA id\n\tf88sm10382106pjg.5.2019.06.30.13.30.07\n\t(version=TLS1_3 cipher=AEAD-AES256-GCM-SHA384 bits=256/256);\n\tSun, 30 Jun 2019 13:30:07 -0700 (PDT)" ], "DKIM-Signature": "v=1; a=rsa-sha256; c=relaxed/relaxed;\n\td=networkplumber-org.20150623.gappssmtp.com; s=20150623;\n\th=date:from:to:cc:subject:message-id:in-reply-to:references\n\t:mime-version:content-transfer-encoding;\n\tbh=vOcD4KJoFuaNJ1oYLFWZ6v1naY0gO9GSa2jiAMuLlq0=;\n\tb=tLkGT+231tfwP0hTKdWwhwH4hH2RTksfN0RssyTy4mhYKk+pT1+50M5dSykcjBk5+7\n\tCes4t5oO1pvHg/MGsOELIdFawwYSlLCjD464wStoyNXFdt3doSC/EPgpteZ5G5xMq+Dz\n\thfYyZMTi0JHSGl2Mw4eiwiQE0Vl2Bvf/PpcBnkUo85oNQgx3qcwUSFCpIr4EMLV3WNLX\n\t2+q+W1WgknqrJZVoM9sRLn/tAt9XfGqMj6Fos/p9HSZcX55GqbElTbxBcD2ILdcG4wBf\n\ty78RQBlaQNYX5c9ugzlT/VVOf6gKcgjiQsTEemDkBsuFLzQeSA4NOoIwxihBotCLr6ZG\n\tdkxg==", "X-Google-DKIM-Signature": "v=1; a=rsa-sha256; c=relaxed/relaxed;\n\td=1e100.net; s=20161025;\n\th=x-gm-message-state:date:from:to:cc:subject:message-id:in-reply-to\n\t:references:mime-version:content-transfer-encoding;\n\tbh=vOcD4KJoFuaNJ1oYLFWZ6v1naY0gO9GSa2jiAMuLlq0=;\n\tb=g5OvME8Xr2ciym3WedjSWYuLOCuPhcxcfkpEO6uBGQrKR66Gnbb1onzNIStUvpSnjD\n\toYjqoTO/KsYVvPmWNSFa07cnf62qKFmivh04vrsWZHPSY4bSpk6/HWbQB0yaBibubX4O\n\tJjCeTlnljWfJlL3r1uLiLYoXbA0WufpMCiC+43AUPZGGERnMLtN0yRz1uIP1AjrIV8eW\n\tXSCt8PqPo4CGJaGcAQUyII0zzjNMxzBpc0EnGeeEOuW9tvif1UCLDU6UQF/Zi1M+Teb9\n\ttKSCDeRmDltQzn7+k9OXexUxSyxMz6sd7+z82JRwQnocoohhXrb4E4vc/V5qh/vK2zgU\n\tRSPg==", "X-Gm-Message-State": "APjAAAVITnTir2v+laE20V0qwZjCGxxcdyoNgM0Dbeqnd7dmnHcOMJEL\n\tG60mY6puvVzmIg4R3mVUUoIRKQ==", "X-Google-Smtp-Source": "APXvYqwl1Za6IqFpHD5shzD8g7aoeFRiuXoUV8/WqT4F+H0FU73HyaIzrx6k8JGd0wPHe91l14LWyw==", "X-Received": "by 2002:a17:902:f301:: with SMTP id\n\tgb1mr24349952plb.292.1561926607818; \n\tSun, 30 Jun 2019 13:30:07 -0700 (PDT)", "Date": "Sun, 30 Jun 2019 13:29:58 -0700", "From": "Stephen Hemminger <stephen@networkplumber.org>", "To": "Gavin Hu <gavin.hu@arm.com>", "Cc": "dev@dpdk.org, thomas@monjalon.net, jerinj@marvell.com,\n\themant.agrawal@nxp.com, bruce.richardson@intel.com,\n\tchaozhu@linux.vnet.ibm.com, Honnappa.Nagarahalli@arm.com, nd@arm.com", "Message-ID": "<20190630132958.6d2250da@hermes.lan>", "In-Reply-To": "<1561911676-37718-1-git-send-email-gavin.hu@arm.com>", "References": "<1561911676-37718-1-git-send-email-gavin.hu@arm.com>", "MIME-Version": "1.0", "Content-Type": "text/plain; charset=US-ASCII", "Content-Transfer-Encoding": "7bit", "Subject": "Re: [dpdk-dev] [RFC 0/5] use WFE for locks and ring on aarch64", "X-BeenThere": "dev@dpdk.org", "X-Mailman-Version": "2.1.15", "Precedence": "list", "List-Id": "DPDK patches and discussions <dev.dpdk.org>", "List-Unsubscribe": "<https://mails.dpdk.org/options/dev>,\n\t<mailto:dev-request@dpdk.org?subject=unsubscribe>", "List-Archive": "<http://mails.dpdk.org/archives/dev/>", "List-Post": "<mailto:dev@dpdk.org>", "List-Help": "<mailto:dev-request@dpdk.org?subject=help>", "List-Subscribe": "<https://mails.dpdk.org/listinfo/dev>,\n\t<mailto:dev-request@dpdk.org?subject=subscribe>", "Errors-To": "dev-bounces@dpdk.org", "Sender": "\"dev\" <dev-bounces@dpdk.org>" }, "addressed": null }, { "id": 97848, "web_url": "http://patches.dpdk.org/comment/97848/", "msgid": "<VI1PR08MB3167E6F95685A13D618BE8F48FF90@VI1PR08MB3167.eurprd08.prod.outlook.com>", "list_archive_url": "https://inbox.dpdk.org/dev/VI1PR08MB3167E6F95685A13D618BE8F48FF90@VI1PR08MB3167.eurprd08.prod.outlook.com", "date": "2019-07-01T09:12:47", "subject": "Re: [dpdk-dev] [RFC 0/5] use WFE for locks and ring on aarch64", "submitter": { "id": 1018, "url": "http://patches.dpdk.org/api/people/1018/?format=api", "name": "Gavin Hu", "email": "gavin.hu@arm.com" }, "content": "Hi Stephen,\n\n> -----Original Message-----\n> From: Stephen Hemminger <stephen@networkplumber.org>\n> Sent: Monday, July 1, 2019 4:30 AM\n> To: Gavin Hu (Arm Technology China) <Gavin.Hu@arm.com>\n> Cc: dev@dpdk.org; thomas@monjalon.net; jerinj@marvell.com;\n> hemant.agrawal@nxp.com; bruce.richardson@intel.com;\n> chaozhu@linux.vnet.ibm.com; Honnappa Nagarahalli\n> <Honnappa.Nagarahalli@arm.com>; nd <nd@arm.com>\n> Subject: Re: [dpdk-dev] [RFC 0/5] use WFE for locks and ring on aarch64\n> \n> On Mon, 1 Jul 2019 00:21:11 +0800\n> Gavin Hu <gavin.hu@arm.com> wrote:\n> \n> > DPDK has multiple use cases where the core repeatedly polls a location in\n> > memory. This polling results in many cache and memory transactions.\n> >\n> > Arm architecture provides WFE (Wait For Event) instruction, which allows\n> > the cpu core to enter a low power state until woken up by the update to the\n> > memory location being polled. Thus reducing the cache and memory\n> > transactions.\n> >\n> > x86 has the PAUSE hint instruction to reduce such overhead.\n> >\n> > The rte_wait_until_equal_xxx APIs abstract the functionality of 'polling\n> > for a memory location to become equal to a given value'.\n> >\n> > For non-Arm platforms, these APIs are just wrappers around do-while loop\n> > with rte_pause, so there are no performance differences.\n> >\n> > For Arm platforms, use of WFE can be configured using\n> CONFIG_RTE_USE_WFE\n> > option. It is disabled by default.\n> >\n> > Currently, use of WFE is supported only for aarch64 platforms. armv7\n> > platforms do support the WFE instruction, but they require explicit wake up\n> > events(sev) and are less performannt.\n> >\n> > Testing shows that, performance varies across different platforms, with\n> > some showing degradation.\n> >\n> > CONFIG_RTE_USE_WFE should be enabled depending on the performance\n> on the\n> > target platforms.\n> \n> How does this work if process is preempted?\nWFE won't prevent pre-emption from the kernel as that is down to a timer/re-scheduling interrupt.\nSoftware using the WFE mechanism must tolerate spurious wake-up events, including timer/re-scheduling interrupts, so a re-check of the condition upon exit of WFE is needed to be in place(this is already included in the patch)", "headers": { "Return-Path": "<dev-bounces@dpdk.org>", "X-Original-To": "patchwork@dpdk.org", "Delivered-To": "patchwork@dpdk.org", "Received": [ "from [92.243.14.124] (localhost [127.0.0.1])\n\tby dpdk.org (Postfix) with ESMTP id 92B752C38;\n\tMon, 1 Jul 2019 11:12:49 +0200 (CEST)", "from EUR02-VE1-obe.outbound.protection.outlook.com\n\t(mail-eopbgr20051.outbound.protection.outlook.com [40.107.2.51])\n\tby dpdk.org (Postfix) with ESMTP id 1E43C2BC8\n\tfor <dev@dpdk.org>; Mon, 1 Jul 2019 11:12:49 +0200 (CEST)", "from VI1PR08MB3167.eurprd08.prod.outlook.com (52.133.15.142) by\n\tVI1PR08MB2781.eurprd08.prod.outlook.com (10.170.236.142) with\n\tMicrosoft SMTP Server (version=TLS1_2,\n\tcipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id\n\t15.20.2008.16; Mon, 1 Jul 2019 09:12:47 +0000", "from VI1PR08MB3167.eurprd08.prod.outlook.com\n\t([fe80::f1a9:e870:d495:8d31]) by\n\tVI1PR08MB3167.eurprd08.prod.outlook.com\n\t([fe80::f1a9:e870:d495:8d31%5]) with mapi id 15.20.2032.019;\n\tMon, 1 Jul 2019 09:12:47 +0000" ], "ARC-Seal": "i=1; a=rsa-sha256; s=testarcselector01; d=microsoft.com; cv=none; \n\tb=bqTZxAlkDL0e3Wt1inAOTIpUsuwBZDx6Y5GuqbW4MKx6l0vkxYrPblbjLIWThJf0wdNNDiqJjUMEQul8e4314dEaEWKW/X08q+8Rtf0Ch0uZmtpdIoeasPYnaawpzZ63HFmF6XtWtHzp9rxV8V/4skTmBW9VkBfInpqaiyzY8Xw=", "ARC-Message-Signature": "i=1; a=rsa-sha256; c=relaxed/relaxed; d=microsoft.com;\n\ts=testarcselector01;\n\th=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck;\n\tbh=pCPH4/BCgZ7BuASV8kNWqnxfK0KuGQJCZY0prfC4kuc=;\n\tb=irW91CfRkWx9lrFZyDbqlNpImq9G3gYKwjDn9S7MF51Ymy8KEGu7YLxrdlBG/X3B9jQSSwxyq43KKOlP619LujaAz0cfMWBpRInjSGMaZAuPA6xyu5+e4SIAyzk2Jek7SL+c4KcAJ+MX8R1+cBO/hzyCoeRFFkhRct/KHe+hgMg=", "ARC-Authentication-Results": "i=1; test.office365.com\n\t1;spf=none;dmarc=none;dkim=none;arc=none", "DKIM-Signature": "v=1; a=rsa-sha256; c=relaxed/relaxed; d=armh.onmicrosoft.com;\n\ts=selector2-armh-onmicrosoft-com;\n\th=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck;\n\tbh=pCPH4/BCgZ7BuASV8kNWqnxfK0KuGQJCZY0prfC4kuc=;\n\tb=7sOpsmm6MxAExlOjbXK5ACdmnCdy1B32UrmgpYs4xna8wQOj7XqL5DxlVaItwSrVmxWwzA+c8Q4z3PishJFjHRaDgDG1hkxsnT1Zgh/C94AlxBc1wEDmNN2mcwA3LaPS+2UiAPirzkom80ntM11bqzx/pRoYhCzEnzzG/JS9zDI=", "From": "\"Gavin Hu (Arm Technology China)\" <Gavin.Hu@arm.com>", "To": "Stephen Hemminger <stephen@networkplumber.org>", "CC": "\"dev@dpdk.org\" <dev@dpdk.org>, \"thomas@monjalon.net\"\n\t<thomas@monjalon.net>, \"jerinj@marvell.com\" <jerinj@marvell.com>,\n\t\"hemant.agrawal@nxp.com\" <hemant.agrawal@nxp.com>,\n\t\"bruce.richardson@intel.com\" <bruce.richardson@intel.com>,\n\t\"chaozhu@linux.vnet.ibm.com\" <chaozhu@linux.vnet.ibm.com>, Honnappa\n\tNagarahalli <Honnappa.Nagarahalli@arm.com>, nd <nd@arm.com>", "Thread-Topic": "[dpdk-dev] [RFC 0/5] use WFE for locks and ring on aarch64", "Thread-Index": "AQHVL1/necIdoVX7bUye4x3mxe47Aaa0pmsAgADS1UA=", "Date": "Mon, 1 Jul 2019 09:12:47 +0000", "Message-ID": "<VI1PR08MB3167E6F95685A13D618BE8F48FF90@VI1PR08MB3167.eurprd08.prod.outlook.com>", "References": "<1561911676-37718-1-git-send-email-gavin.hu@arm.com>\n\t<20190630132958.6d2250da@hermes.lan>", "In-Reply-To": "<20190630132958.6d2250da@hermes.lan>", "Accept-Language": "en-US", "Content-Language": "en-US", "X-MS-Has-Attach": "", "X-MS-TNEF-Correlator": "", "x-ts-tracking-id": "183c812a-73f2-47ff-be1e-1cbab80f71c4.0", "x-checkrecipientchecked": "true", "authentication-results": "spf=none (sender IP is )\n\tsmtp.mailfrom=Gavin.Hu@arm.com; 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SFP:1101; SCL:1; SRVR:VI1PR08MB2781;\n\tH:VI1PR08MB3167.eurprd08.prod.outlook.com; FPR:; SPF:None; LANG:en;\n\tPTR:InfoNoRecords; A:1; MX:1; ", "received-spf": "None (protection.outlook.com: arm.com does not designate\n\tpermitted sender hosts)", "x-ms-exchange-senderadcheck": "1", "x-microsoft-antispam-message-info": "t2RWvGANLXRbLSYvWq2SrCf7BNN2UV2dKj9f5xQp3ET3Bif1NzzmplL2QdDelbo2oFbxLxyut1Fjy642E5KTGStAkqwMJcsea8IPpvmMls5HJHGTN1M3PV7zQLE3pvhhXtA+SBQ9/WcDLvsIxJUSlyGcWhSPUitULfGoL97W32IM3E7kvQgYnbtnHNZijP039RlpJziJf7HZfi/sftswezJMgVDCK4HqE3SCwOJlhtaSP3/1OBTPVwysEbn6GArQdZHQDSsWgNQDPItoqe8SRTtUTNaVtwb91hByyGsS+6NgQwz6PM/yoNgzxiLyz6Fi2ZhyIKndnuMP1s/+0Yjf21qJV6IwdjS8LyEgTFOOqnab9uZ9k2vLP9+q8h87oqaJf7Va5QvVubYed10vgVItR7r967KlArFK080Y9hPN9x8=", "Content-Type": "text/plain; charset=\"us-ascii\"", "Content-Transfer-Encoding": "quoted-printable", "MIME-Version": "1.0", "X-OriginatorOrg": "arm.com", "X-MS-Exchange-CrossTenant-Network-Message-Id": "a699d049-ec11-49d0-32bf-08d6fe0448db", "X-MS-Exchange-CrossTenant-originalarrivaltime": "01 Jul 2019 09:12:47.4073\n\t(UTC)", "X-MS-Exchange-CrossTenant-fromentityheader": "Hosted", "X-MS-Exchange-CrossTenant-id": "f34e5979-57d9-4aaa-ad4d-b122a662184d", "X-MS-Exchange-CrossTenant-mailboxtype": "HOSTED", "X-MS-Exchange-CrossTenant-userprincipalname": "Gavin.Hu@arm.com", "X-MS-Exchange-Transport-CrossTenantHeadersStamped": "VI1PR08MB2781", "Subject": "Re: [dpdk-dev] [RFC 0/5] use WFE for locks and ring on aarch64", "X-BeenThere": "dev@dpdk.org", "X-Mailman-Version": "2.1.15", "Precedence": "list", "List-Id": "DPDK patches and discussions <dev.dpdk.org>", "List-Unsubscribe": "<https://mails.dpdk.org/options/dev>,\n\t<mailto:dev-request@dpdk.org?subject=unsubscribe>", "List-Archive": "<http://mails.dpdk.org/archives/dev/>", "List-Post": "<mailto:dev@dpdk.org>", "List-Help": "<mailto:dev-request@dpdk.org?subject=help>", "List-Subscribe": "<https://mails.dpdk.org/listinfo/dev>,\n\t<mailto:dev-request@dpdk.org?subject=subscribe>", "Errors-To": "dev-bounces@dpdk.org", "Sender": "\"dev\" <dev-bounces@dpdk.org>" }, "addressed": null } ]