From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mga01.intel.com (mga01.intel.com [192.55.52.88]) by dpdk.org (Postfix) with ESMTP id 1AAD88D3D for ; Tue, 27 Oct 2015 20:35:32 +0100 (CET) Received: from fmsmga003.fm.intel.com ([10.253.24.29]) by fmsmga101.fm.intel.com with ESMTP; 27 Oct 2015 12:10:13 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.20,206,1444719600"; d="scan'208";a="589124852" Received: from irsmsx108.ger.corp.intel.com ([163.33.3.3]) by FMSMGA003.fm.intel.com with ESMTP; 27 Oct 2015 12:10:11 -0700 Received: from irsmsx105.ger.corp.intel.com ([169.254.7.75]) by IRSMSX108.ger.corp.intel.com ([169.254.11.138]) with mapi id 14.03.0248.002; Tue, 27 Oct 2015 19:10:09 +0000 From: "Ananyev, Konstantin" To: Vlad Zolotarov , Thomas Monjalon , "Zhang, Helin" Thread-Topic: [dpdk-dev] [PATCH v4] ixgbe_pmd: enforce RS bit on every EOP descriptor for devices newer than 82598 Thread-Index: AQHQ3kSTdryx3Zz46keR7eksKu4ZCZ6ACKmAgAAKwACAAAEVYA== Date: Tue, 27 Oct 2015 19:10:10 +0000 Message-ID: <2601191342CEEE43887BDE71AB97725836AB5A51@irsmsx105.ger.corp.intel.com> References: <1440085070-13989-1-git-send-email-vladz@cloudius-systems.com> <55DAD1C9.3010802@cloudius-systems.com> <1764015.lv7zT9MUyf@xps13> <562FC6D4.8000202@cloudius-systems.com> In-Reply-To: <562FC6D4.8000202@cloudius-systems.com> Accept-Language: en-IE, en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-originating-ip: [163.33.239.180] Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 Cc: "dev@dpdk.org" , "Kirsher, Jeffrey T" , "Brandeburg, Jesse" Subject: Re: [dpdk-dev] [PATCH v4] ixgbe_pmd: enforce RS bit on every EOP descriptor for devices newer than 82598 X-BeenThere: dev@dpdk.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: patches and discussions about DPDK List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 27 Oct 2015 19:35:33 -0000 Hi lads, > -----Original Message----- > From: Vlad Zolotarov [mailto:vladz@cloudius-systems.com] > Sent: Tuesday, October 27, 2015 6:48 PM > To: Thomas Monjalon; Ananyev, Konstantin; Zhang, Helin > Cc: dev@dpdk.org; Kirsher, Jeffrey T; Brandeburg, Jesse > Subject: Re: [dpdk-dev] [PATCH v4] ixgbe_pmd: enforce RS bit on every EOP= descriptor for devices newer than 82598 >=20 >=20 >=20 > On 10/27/15 20:09, Thomas Monjalon wrote: > > Any Follow-up to this discussion? > > Should we mark this patch as rejected? >=20 > Hmmm... This patch fixes an obvious spec violation. Why would it be > rejected? No I don't think we can reject the patch: There is a reproducible TX hang on ixgbe PMD on described conditions. Though, as I explained here: http://dpdk.org/ml/archives/dev/2015-September/023574.html Vlad's patch would cause quite a big slowdown. We are still in the process to get an answer from HW guys are there any alternatives that will allow to fix the problem and avoid the slowdown. Konstantin =20 >=20 > > > > 2015-08-24 11:11, Vlad Zolotarov: > >> On 08/20/15 18:37, Vlad Zolotarov wrote: > >>> According to 82599 and x540 HW specifications RS bit *must* be > >>> set in the last descriptor of *every* packet. > >>> > >>> Before this patch there were 3 types of Tx callbacks that were settin= g > >>> RS bit every tx_rs_thresh descriptors. This patch introduces a set of > >>> new callbacks, one for each type mentioned above, that will set the R= S > >>> bit in every EOP descriptor. > >>> > >>> ixgbe_set_tx_function() will set the appropriate Tx callback accordin= g > >>> to the device family. > >> [+Jesse and Jeff] > >> > >> I've started to look at the i40e PMD and it has the same RS bit > >> deferring logic > >> as ixgbe PMD has (surprise, surprise!.. ;)). To recall, i40e PMD uses = a > >> descriptor write-back > >> completion mode. > >> > >> From the HW Spec it's unclear if RS bit should be set on *every* des= criptor > >> with EOP bit. However I noticed that Linux driver, before it moved to > >> HEAD write-back mode, was setting RS > >> bit on every EOP descriptor. > >> > >> So, here is a question to Intel guys: could u, pls., clarify this poin= t? > >> > >> Thanks in advance, > >> vlad > > > >