Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Date:   Wed, 12 Apr 2023 13:02:45 -0300
From:   Jason Gunthorpe <jgg@nvidia.com>
To:     Christophe JAILLET <christophe.jaillet@wanadoo.fr>,
        Shiraz Saleem <shiraz.saleem@intel.com>
Cc:     Mustafa Ismail <mustafa.ismail@intel.com>,
        Leon Romanovsky <leon@kernel.org>,
        linux-kernel@vger.kernel.org, kernel-janitors@vger.kernel.org,
        linux-rdma@vger.kernel.org
Subject: Re: [PATCH] RDMA/irdma: Slightly optimize irdma_form_ah_cm_frame()
Message-ID: <ZDbWJcqTbCducrUO@nvidia.com>
References: <098e3c397be0436f1867899245ecfe656c472110.1675369386.git.christophe.jaillet@wanadoo.fr>
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <098e3c397be0436f1867899245ecfe656c472110.1675369386.git.christophe.jaillet@wanadoo.fr>
MIME-Version: 1.0
X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1
X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?WtS9lEWireQZ73iSFMkiVztFqHn1iQl/EnDmIBIdRmTHoDoPXZ5awdxl3VRi?=
 =?us-ascii?Q?ReVghe7nmM69IuRKbjBplktNgzadoMBhOT6xoYCfSCSKOUiJxe+QEDTx2Loh?=
 =?us-ascii?Q?8hovXyCe8aysFeWdTa9KGpoc6sMH7ZkJXgK3AM1JGgJWqLVBjwiFnFmbwzun?=
 =?us-ascii?Q?hH8i5ZbU1uJ2C1T/LxtsK5q0+JApiP2CxdSj7ZILDGKMY9hcEj9Oz8ttgzgn?=
 =?us-ascii?Q?ksFRXxOIvVySjEnvxik1KeSuwGXZ7cWJljYTGaR+bWK1MQ9UUgIy5VrJG/Ri?=
 =?us-ascii?Q?2QVX4BI9bJT3Kmrlq8cwKf3Aub38fsai2ern5IOi94NXyMmWgzNYLGs/NQZR?=
 =?us-ascii?Q?wNVvOryp+wevgrj5nFV0RYStCV+Ey97BA3+Fla+NEtu51sFqB3YDIfA37uSF?=
 =?us-ascii?Q?stu51/Mt+QmDDJLE86pzk3ZOLug4mjliOCmBA7NG1Zk/24GEC65j0xVhM4PZ?=
 =?us-ascii?Q?S1+jozol6IA+xNHkjnepgewVjSNgKr8Gp+0lDITV7P+PaFqdzjUaDLCuc08m?=
 =?us-ascii?Q?1pgkVFh2G2gykvSWOJagdLmfwQ/G0833CBzZOwxUcZcpnsUU5++dCUU00Ipl?=
 =?us-ascii?Q?CvtsYzHmKjrrLOGeTOXykHastXQf4qNx/wjTEeC4Ht7eij9pcICbViuRKHCy?=
 =?us-ascii?Q?tgG+k9RCHHHuL+6Hdi3PvQ61XOrPVY9Fuplgbw1TuKxQ7IwI3HV6I3Mec3sZ?=
 =?us-ascii?Q?kplxELe6YeIkPr2OLYHKtylCzbEtWpZO+s4IX8+XRF6/8YvCoQhM6E+sAC2E?=
 =?us-ascii?Q?nkXBZ/H+Uf8xRb8BqVxtZM+iHr7ptD+Z3MISH3EJKKq3IJvPT/sklrX59FKd?=
 =?us-ascii?Q?JPkLI2nzroc/jJIZLpjk63+PRxXHSr7EtgZdz/iVkeZv6r5BzTC5qVZCXp+B?=
 =?us-ascii?Q?4LA/Ea8nhKuQD+ufJNyAuqJEgyClo21czx3hl6yxIW3OoImGMhB5LTTaSe7H?=
 =?us-ascii?Q?kB5zN8eFVwFWyGwxr0V7lSUfbuwJ2Ev/tEujn+x9HYFpLc/ZfTxiVJE2LM4w?=
 =?us-ascii?Q?qrWqDM46tZnPwuogPB6iKzn2XXGfIQDlcqy+WeDG4SkFGUidzOVx/j6Zg/Di?=
 =?us-ascii?Q?mJMdBldiE1gyZgTFddYy8J1Syy/Y7AVGTVvvj3rfxC574KLKmb7HOrjY2IYp?=
 =?us-ascii?Q?nJfrS4mAJCU2xRGz5ioZS2tXOMkzC0lGL4tKetKYp4/vOuCA4Mdu+xdKE8d5?=
 =?us-ascii?Q?t/vhpoKAyb6N6wlJ/DREAeLOndhrpmi4RzR3nDW19yi3qQtYAGuRkzFRBLj4?=
 =?us-ascii?Q?Qp6XyhGwtuUvjlumNqTWt3brEChYak8N0zQxgGkZ306D6pJvY4LLtjGQeUrM?=
 =?us-ascii?Q?/dM36vIVSNSNDAedzMIoL8z2V5pGduKPhYv/2//CM0orw/B3rW6nVP8QbJpR?=
 =?us-ascii?Q?gXmY7UA9TyyllX5XmyaTfhy7yhS8jXNku4M7FTLjhF53D7i4zCQOprKGstly?=
 =?us-ascii?Q?ZjSUJ/K8toR5Dv0WZOxNK9KVpOMSlYMxYnytoLzBqDpb5zsdC95Gq7bxCHrR?=
 =?us-ascii?Q?lA/vvbryhkszwFx2qCaTiusdxUufKN6GbSmprkztxjw/AVHMU5M/VTcHccpm?=
 =?us-ascii?Q?eooeFXdAAz93WVRKE7Dzq+0dPLk74sB2/CQFT+4j?=
X-OriginatorOrg: Nvidia.com
X-MS-Exchange-CrossTenant-Network-Message-Id: 78fea878-1b3b-4048-0f8b-08db3b6f5cc8
X-MS-Exchange-CrossTenant-AuthSource: LV2PR12MB5869.namprd12.prod.outlook.com
X-MS-Exchange-CrossTenant-AuthAs: Internal
X-MS-Exchange-CrossTenant-OriginalArrivalTime: 12 Apr 2023 16:02:49.2244
 (UTC)
X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted
X-MS-Exchange-CrossTenant-Id: 43083d15-7273-40c1-b7db-39efd9ccc17a
X-MS-Exchange-CrossTenant-MailboxType: HOSTED
X-MS-Exchange-CrossTenant-UserPrincipalName: Mab/wJt6hJokOfjuDfbdpKHwZTbvZ5Po3y1/r9f4O8bkEo8hnqImHrPPlzZo/6aQ
X-MS-Exchange-Transport-CrossTenantHeadersStamped: SA3PR12MB7879
X-Spam-Status: No, score=-1.1 required=5.0 tests=BAYES_00,DKIMWL_WL_HIGH,
        DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,FORGED_SPF_HELO,
        RCVD_IN_DNSWL_NONE,RCVD_IN_MSPIKE_H2,SPF_HELO_PASS,SPF_NONE,
        URIBL_BLOCKED autolearn=no autolearn_force=no version=3.4.6
X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on
        lindbergh.monkeyblade.net
Precedence: bulk
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

On Thu, Feb 02, 2023 at 09:23:24PM +0100, Christophe JAILLET wrote:
> There is no need to zero 'pktsize' bytes of 'buf', only the header needs
> to be cleared, to be safe.
> All the other bytes are already written with some memcpy() at the end of
> the function.
> 
> Doing so also gives the opportunity to the compiler to avoid the memset()
> call. It can be inlined now that the length is known as compile time.
> 
> Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
> ---
> Just in case, here is the diff of what is generated by gcc 11.3.0 before
> and after the patch.
> 
>  .L736:
> -# drivers/infiniband/hw/irdma/cm.c:340: 	memset(buf, 0, pktsize);
> +# drivers/infiniband/hw/irdma/cm.c:340: 	memset(buf, 0, sizeof(*tcph));
>  	call	__sanitizer_cov_trace_pc	#
> -	xorl	%esi, %esi	#
> -	movzwl	%r13w, %edx	# _194, __fortify_size
> -	movq	%rbp, %rdi	# buf,
> -	call	memset	#
> -	leaq	104(%r12), %rax	#, _259
> +	movl	$0, 16(%rbp)	#, MEM <char[1:20]> [(void *)buf_114]
> +	leaq	104(%r12), %rax	#, _295
> +# drivers/infiniband/hw/irdma/cm.c:342: 	sqbuf->totallen = pktsize;
> +	movzwl	%r13w, %r13d	# _192, _192
> +# drivers/infiniband/hw/irdma/cm.c:340: 	memset(buf, 0, sizeof(*tcph));
> +	movq	$0, 0(%rbp)	#, MEM <char[1:20]> [(void *)buf_114]
> +# drivers/infiniband/hw/irdma/cm.c:342: 	sqbuf->totallen = pktsize;
> +	movq	%rax, %rdi	# _295,
> +# drivers/infiniband/hw/irdma/cm.c:340: 	memset(buf, 0, sizeof(*tcph));
> +	movq	$0, 8(%rbp)	#, MEM <char[1:20]> [(void *)buf_114]
> +	movq	%rax, 64(%rsp)	# _295, %sfp
>  # drivers/infiniband/hw/irdma/cm.c:342: 	sqbuf->totallen = pktsize;
> ---
>  drivers/infiniband/hw/irdma/cm.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)

Shiraz??

Jason