From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mga18.intel.com (mga18.intel.com [134.134.136.126]) by dpdk.org (Postfix) with ESMTP id 662A3DE0 for ; Fri, 25 May 2018 14:18:48 +0200 (CEST) X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga007.fm.intel.com ([10.253.24.52]) by orsmga106.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 25 May 2018 05:18:46 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.49,440,1520924400"; d="scan'208";a="42145898" Received: from aburakov-mobl.ger.corp.intel.com (HELO [10.237.220.101]) ([10.237.220.101]) by fmsmga007.fm.intel.com with ESMTP; 25 May 2018 05:18:44 -0700 To: Olivier Matz , dev@dpdk.org, "Ananyev, Konstantin" , "Richardson, Bruce" References: <20170630142609.6180-1-olivier.matz@6wind.com> <20180403132644.23729-1-olivier.matz@6wind.com> <460fd61f-4346-752b-02c9-5ac952ea5215@intel.com> From: "Burakov, Anatoly" Message-ID: Date: Fri, 25 May 2018 13:18:44 +0100 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:52.0) Gecko/20100101 Thunderbird/52.7.0 MIME-Version: 1.0 In-Reply-To: <460fd61f-4346-752b-02c9-5ac952ea5215@intel.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit Subject: Re: [dpdk-dev] [PATCH] ring: relax alignment constraint on ring structure 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: Fri, 25 May 2018 12:18:48 -0000 On 25-May-18 11:59 AM, Burakov, Anatoly wrote: > On 03-Apr-18 2:26 PM, Olivier Matz wrote: >> The initial objective of >> commit d9f0d3a1ffd4 ("ring: remove split cacheline build setting") >> was to add an empty cache line betwee, the producer and consumer >> data (on platform with cache line size = 64B), preventing from >> having them on adjacent cache lines. >> >> Following discussion on the mailing list, it appears that this >> also imposes an alignment constraint that is not required. >> >> This patch removes the extra alignment constraint and adds the >> empty cache lines using padding fields in the structure. The >> size of rte_ring structure and the offset of the fields remain >> the same on platforms with cache line size = 64B: >> >>    rte_ring = 384 >>    rte_ring.name = 0 >>    rte_ring.flags = 32 >>    rte_ring.memzone = 40 >>    rte_ring.size = 48 >>    rte_ring.mask = 52 >>    rte_ring.prod = 128 >>    rte_ring.cons = 256 >> >> But it has an impact on platform where cache line size is 128B: >> >>    rte_ring = 384        -> 768 >>    rte_ring.name = 0 >>    rte_ring.flags = 32 >>    rte_ring.memzone = 40 >>    rte_ring.size = 48 >>    rte_ring.mask = 52 >>    rte_ring.prod = 128   -> 256 >>    rte_ring.cons = 256   -> 512 >> >> Link: http://dpdk.org/dev/patchwork/patch/25039/ >> Suggested-by: Konstantin Ananyev >> Signed-off-by: Olivier Matz >> --- > > This patch causes eal_flags_autotest to hang on FreeBSD. Root cause at > this time is unknown, but this is a weird one - the test seems to hang > while doing read() in bsd/eal_thread.c:59. Reverting this patch on top > of rc5 results in eal_flags_autotest passing. > Further investigation shows that for some reason, if Enter is pressed while the test is seemingly "hung", it continues and passes. Or rather, it hangs on one test, and if Enter is pressed, it finishes that test and hangs on another, after which pressing Enter again will result in test succeeding. Weird... -- Thanks, Anatoly