From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from mails.dpdk.org (mails.dpdk.org [217.70.189.124]) by smtp.lore.kernel.org (Postfix) with ESMTP id CEB46C54E66 for ; Fri, 15 Mar 2024 08:31:59 +0000 (UTC) Received: from mails.dpdk.org (localhost [127.0.0.1]) by mails.dpdk.org (Postfix) with ESMTP id 0245342DCA; Fri, 15 Mar 2024 09:31:59 +0100 (CET) Received: from szxga04-in.huawei.com (szxga04-in.huawei.com [45.249.212.190]) by mails.dpdk.org (Postfix) with ESMTP id 378514027B; Fri, 15 Mar 2024 09:31:56 +0100 (CET) Received: from mail.maildlp.com (unknown [172.19.162.112]) by szxga04-in.huawei.com (SkyGuard) with ESMTP id 4Twy8j09fwz2BgPh; Fri, 15 Mar 2024 16:29:25 +0800 (CST) Received: from dggpeml500024.china.huawei.com (unknown [7.185.36.10]) by mail.maildlp.com (Postfix) with ESMTPS id F1E651402C7; Fri, 15 Mar 2024 16:31:53 +0800 (CST) Received: from [10.67.121.161] (10.67.121.161) by dggpeml500024.china.huawei.com (7.185.36.10) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.1.2507.35; Fri, 15 Mar 2024 16:31:53 +0800 Subject: Re: [PATCH v2] dmadev: fix structure alignment To: "Ma, WenwuX" , "dev@dpdk.org" CC: "Jiale, SongX" , "stable@dpdk.org" References: <20240308053711.1260154-1-wenwux.ma@intel.com> <20240315014331.1376720-1-wenwux.ma@intel.com> <096d2161-026c-f89e-c44b-340a3148bccc@huawei.com> From: fengchengwen Message-ID: Date: Fri, 15 Mar 2024 16:31:53 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:68.0) Gecko/20100101 Thunderbird/68.11.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset="utf-8" Content-Language: en-US Content-Transfer-Encoding: 8bit X-Originating-IP: [10.67.121.161] X-ClientProxiedBy: dggems702-chm.china.huawei.com (10.3.19.179) To dggpeml500024.china.huawei.com (7.185.36.10) X-BeenThere: dev@dpdk.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: DPDK patches and discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dev-bounces@dpdk.org Hi Wenwu, On 2024/3/15 15:44, Ma, WenwuX wrote: > Hi Chengwen, > >> -----Original Message----- >> From: Ma, WenwuX >> Sent: Friday, March 15, 2024 2:26 PM >> To: fengchengwen ; dev@dpdk.org >> Cc: Jiale, SongX ; stable@dpdk.org >> Subject: RE: [PATCH v2] dmadev: fix structure alignment >> >> Hi Chengwen, >> >>> -----Original Message----- >>> From: fengchengwen >>> Sent: Friday, March 15, 2024 2:06 PM >>> To: Ma, WenwuX ; dev@dpdk.org >>> Cc: Jiale, SongX ; stable@dpdk.org >>> Subject: Re: [PATCH v2] dmadev: fix structure alignment >>> >>> Hi Wenwu, >>> >>> On 2024/3/15 9:43, Wenwu Ma wrote: >>>> The structure rte_dma_dev needs only 8 byte alignment. >>>> This patch replaces __rte_cache_aligned of rte_dma_dev with >>>> __rte_aligned(8). >>>> >>>> Fixes: b36970f2e13e ("dmadev: introduce DMA device library") >>>> Cc: stable@dpdk.org >>>> >>>> Signed-off-by: Wenwu Ma >>>> --- >>>> v2: >>>> - Because of performance drop, adjust the code to >>>> no longer demand cache line alignment >>> >>> Which two versions observed performance drop? And which benchmark >>> observed drop? >>> Could you provide more information? >>> >>>> >> V1 patch: >> https://patches.dpdk.org/project/dpdk/patch/20240308053711.1260154- >> 1-wenwux.ma@intel.com/ >> >> To view detailed results, visit: >> https://lab.dpdk.org/results/dashboard/patchsets/29472/ >> >>>> --- >>>> lib/dmadev/rte_dmadev_pmd.h | 2 +- >>>> 1 file changed, 1 insertion(+), 1 deletion(-) >>>> >>>> diff --git a/lib/dmadev/rte_dmadev_pmd.h >>> b/lib/dmadev/rte_dmadev_pmd.h >>>> index 58729088ff..b569bb3502 100644 >>>> --- a/lib/dmadev/rte_dmadev_pmd.h >>>> +++ b/lib/dmadev/rte_dmadev_pmd.h >>>> @@ -122,7 +122,7 @@ enum rte_dma_dev_state { >>>> * @internal >>>> * The generic data structure associated with each DMA device. >>>> */ >>>> -struct __rte_cache_aligned rte_dma_dev { >>>> +struct __rte_aligned(8) rte_dma_dev { >>> >>> The DMA fast-path was implemented by struct rte_dma_fp_objs, which is >>> not rte_dma_dev? So why is it a problem here? >>> >>> Thanks >>> >> The DMA device object is expected to align cache line, so clang will use >> “vmovaps” assembly instruction, >> >> And the instruction demands 16 bytes alignment or will cause segment fault in >> some environments. >> > Test case: > 1. compile dpdk > rm -rf x86_64-native-linuxapp-clang > CC=clang meson -Denable_kmods=True -Dlibdir=lib --default-library=static x86_64-native-linuxapp-clang > ninja -C x86_64-native-linuxapp-clang -j 72 > 2. start dpdk-test > /root/dpdk/x86_64-native-linuxapp-clang/app/dpdk-test -l 0-39 --vdev=dma_skeleton -a 31:00.0 -a 31:00.1 -a 31:00.2 -a 31:00.3 （Note: If it cannot be reproduced, please try using a different core） > 3. exit dpdk-test > RTE>>quit > Segmentation fault (core dumped) I will try to reproduce, but still a question: does above test has already merged your patch [1] or the current main branch code has this problem? [1] https://patches.dpdk.org/project/dpdk/patch/20240308053711.1260154-1-wenwux.ma@intel.com/ Thanks > >> >>>> /** Device info which supplied during device initialization. */ >>>> struct rte_device *device; >>>> struct rte_dma_dev_data *data; /**< Pointer to shared device data. >>>> */ >>>>