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 372643251 for ; Tue, 6 Jun 2017 16:56:34 +0200 (CEST) Received: from fmsmga004.fm.intel.com ([10.253.24.48]) by fmsmga101.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 06 Jun 2017 07:56:31 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.39,306,1493708400"; d="scan'208";a="270831165" Received: from bricha3-mobl3.ger.corp.intel.com ([10.237.221.28]) by fmsmga004.fm.intel.com with SMTP; 06 Jun 2017 07:56:29 -0700 Received: by (sSMTP sendmail emulation); Tue, 06 Jun 2017 15:56:29 +0100 Date: Tue, 6 Jun 2017 15:56:28 +0100 From: Bruce Richardson To: "Ananyev, Konstantin" Cc: "Verkamp, Daniel" , "dev@dpdk.org" Message-ID: <20170606145628.GB55760@bricha3-MOBL3.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> <2601191342CEEE43887BDE71AB9772583FB0644D@IRSMSX109.ger.corp.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <2601191342CEEE43887BDE71AB9772583FB0644D@IRSMSX109.ger.corp.intel.com> Organization: Intel Research and =?iso-8859-1?Q?De=ACvel?= =?iso-8859-1?Q?opment?= Ireland Ltd. User-Agent: Mutt/1.8.1 (2017-04-11) 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 14:56:35 -0000 On Tue, Jun 06, 2017 at 02:19:21PM +0100, Ananyev, Konstantin wrote: > > > > -----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 > > > > 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 reason for that? > > > > > Konstantin > > > > > > > > I don't know why PROD_ALIGN/CONS_ALIGN use 128 byte alignment; it seems 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 >= 128-byte alignment logic in rte_ring.h? > > > > > > Might be, would be good to hear opinion the author of that change. > > > > 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-line 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 Sure. That should probably work too. /Bruce