From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mga02.intel.com (mga02.intel.com [134.134.136.20]) by dpdk.org (Postfix) with ESMTP id 361BD4CE4 for ; Tue, 6 Jun 2017 15:19:25 +0200 (CEST) Received: from orsmga001.jf.intel.com ([10.7.209.18]) by orsmga101.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 06 Jun 2017 06:19:24 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.39,306,1493708400"; d="scan'208";a="1138478042" Received: from irsmsx152.ger.corp.intel.com ([163.33.192.66]) by orsmga001.jf.intel.com with ESMTP; 06 Jun 2017 06:19:23 -0700 Received: from irsmsx109.ger.corp.intel.com ([169.254.13.250]) by IRSMSX152.ger.corp.intel.com ([169.254.6.83]) with mapi id 14.03.0319.002; Tue, 6 Jun 2017 14:19:22 +0100 From: "Ananyev, Konstantin" To: "Richardson, Bruce" CC: "Verkamp, Daniel" , "dev@dpdk.org" Thread-Topic: [dpdk-dev] [PATCH v2] ring: use aligned memzone allocation Thread-Index: AQHS29yUGhSpppN6a069aA11FRzec6ISDAhwgAAJcACAANJnAIADf1kAgAE3tZCAAB0sgIAAGAMw Date: Tue, 6 Jun 2017 13:19:21 +0000 Message-ID: <2601191342CEEE43887BDE71AB9772583FB0644D@IRSMSX109.ger.corp.intel.com> References: <20170602200337.50743-1-daniel.verkamp@intel.com> <20170602201213.51143-1-daniel.verkamp@intel.com> <2601191342CEEE43887BDE71AB9772583FB05190@IRSMSX109.ger.corp.intel.com> <2601191342CEEE43887BDE71AB9772583FB05216@IRSMSX109.ger.corp.intel.com> <2601191342CEEE43887BDE71AB9772583FB060FD@IRSMSX109.ger.corp.intel.com> <20170606124201.GA43772@bricha3-MOBL3.ger.corp.intel.com> In-Reply-To: <20170606124201.GA43772@bricha3-MOBL3.ger.corp.intel.com> Accept-Language: en-IE, en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: dlp-product: dlpe-windows dlp-version: 10.0.102.7 dlp-reaction: no-action x-originating-ip: [163.33.239.180] Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 Subject: Re: [dpdk-dev] [PATCH v2] ring: use aligned memzone allocation 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: Tue, 06 Jun 2017 13:19:26 -0000 > -----Original Message----- > From: Richardson, Bruce > Sent: Tuesday, June 6, 2017 1:42 PM > To: Ananyev, Konstantin > Cc: Verkamp, Daniel ; dev@dpdk.org > Subject: Re: [dpdk-dev] [PATCH v2] ring: use aligned memzone allocation >=20 > On Tue, Jun 06, 2017 at 10:59:59AM +0100, Ananyev, Konstantin wrote: > > > > > > > > > > > > > > > > > > > > > > > > The PROD/CONS_ALIGN values on x86-64 are set to 2 cache lines, so= members > > > > of struct rte_ring are 128 byte aligned, > > > > >and therefore the whole struct needs 128-byte alignment according = to the ABI > > > > so that the 128-byte alignment of the fields can be guaranteed. > > > > > > > > Ah ok, missed the fact that rte_ring is 128B aligned these days. > > > > BTW, I probably missed the initial discussion, but what was the rea= son for that? > > > > Konstantin > > > > > > I don't know why PROD_ALIGN/CONS_ALIGN use 128 byte alignment; it see= ms unnecessary if the cache line is only 64 bytes. An > alternate > > > fix would be to just use cache line alignment for these fields (since= memzones are already cache line aligned). > > > > Yes, had the same thought. > > > > > Maybe there is some deeper reason for the >=3D 128-byte alignment lo= gic in rte_ring.h? > > > > Might be, would be good to hear opinion the author of that change. >=20 > It gives improved performance for core-2-core transfer. You mean empty cache-line(s) after prod/cons, correct? That's ok but why we can't keep them and whole rte_ring aligned on cache-li= ne boundaries? Something like that: struct rte_ring { ... struct rte_ring_headtail prod __rte_cache_aligned; EMPTY_CACHE_LINE __rte_cache_aligned; struct rte_ring_headtail cons __rte_cache_aligned; EMPTY_CACHE_LINE __rte_cache_aligned; }; Konstantin