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 20:06:39 -0300
From:   Jason Gunthorpe <jgg@nvidia.com>
To:     Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Cc:     Mustafa Ismail <mustafa.ismail@intel.com>,
        Shiraz Saleem <shiraz.saleem@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: <ZDc5f7SFUhli8T3h@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?NRP/2M5Uk42koIKoLb1mRT5Ujljd4NFq0zkdxj/T3d4B84nSwODS1shbyvR+?=
 =?us-ascii?Q?uFIsop6XS+wWsK7Bx2bJKPsaEiGSbMUSjPb4ltPzaL0qFiRddqbOL3iUxoXS?=
 =?us-ascii?Q?jgYcLLAYpthvEQe3Kd+5zl12TWj6ck31v0QjDZKYJq403CiWZ2W3H4FLEk4o?=
 =?us-ascii?Q?9+suVypkfTd0g3hfPCm8ONqI64oyYm7nUgOaLPxWNzpVZ/dlL70NQpc6A+t6?=
 =?us-ascii?Q?CurllIRdGInlP7ouW2pMMCypzLxou9l0aK5OtgU5YJWcgOCuJAOF28+iZn6z?=
 =?us-ascii?Q?ljroIL4LW0O1rl6HM/aAA3h9AYpgKAUByd2WS6vTeSpezUG4Cxt7sMSe15c0?=
 =?us-ascii?Q?sXHYgl7pZ4fm0aNhLJY0/3yuecBSIuQWNBZQDRczoM+muzfoTDhOgFWMamvY?=
 =?us-ascii?Q?X+EBE06vnKfvuQaKJp9iPp8Vf+jQRk7ZJHCvsheZrfhy+mfOpkHbPE1ZD2sG?=
 =?us-ascii?Q?284brur1/k5AZ5QVw7dePrVPW+fKDKNoPFXsVrjFeilh3kKrxP8uSD3JK1LF?=
 =?us-ascii?Q?VyHdfYd7kyaCkBCRn8Se73TAQ5xGqNo6UrLiR52omoqmNTI/Ug61VBGLcMpw?=
 =?us-ascii?Q?OobRPf9EW+v0q+Fp2anW/oJr0MYdKzZTZXTO9k+ZbiN7OyyEbujGHnQamhVT?=
 =?us-ascii?Q?LJVMwdWrumPlMjIh3y6o/KZJ+ftlfQrzz2VdI+HQr5BpeNtaJIEGcHQ/qnV/?=
 =?us-ascii?Q?k70lYThKMLEU2hfLUHi5QP3sAnW0xzWpE2nDjHAxeAIBgeGIuIKUfLE2xrob?=
 =?us-ascii?Q?90udLxUZR8TzMckq6ARNeKS03jWc67izINDPcmLRRvXODGr9oBMhfzPbN+JA?=
 =?us-ascii?Q?8Ej0Qw7U4POHvjKct/Zkbq9TaCWXNJiRyIrz4zF8ryC1KULXSQm4kChcVbRp?=
 =?us-ascii?Q?VvFBJlerOHgfDve2pI1a6V0cpI2DdmyergdcNsnHwjx2PFhjbS9ZOsOslqgn?=
 =?us-ascii?Q?TTbkDJiB23goQy9e4a6YRcByrwsKK6DHBhc+AoUEy/ymrhafrs2X1tOXaNHL?=
 =?us-ascii?Q?hMQ2Hr+bvr/Gr1SNHNlHbrNIZ5zhij1h5OvUtXIN+dUJl1zIWx1WiwgwU7vl?=
 =?us-ascii?Q?/1fUu10047INHe0vumEQMNtmhjqMkMeS0SjDyUXTIFxbYeWEM/a3OJGpBtAu?=
 =?us-ascii?Q?j/MFDQQCLns6hGnXaMcg+xQWp4PCfKMLLAJs8olOqfxLs05cWvyKEtP+7u0n?=
 =?us-ascii?Q?lansN0VtZGHX6avI6grX0dvraKysCIR2njLEexQF2P0f+KYt9mLAlpOycIsZ?=
 =?us-ascii?Q?Ey532G4m3di04j9/zlKtmoTzdXfkiYiQFvYdauE4p9TQz0aok5YgwqXQHmiU?=
 =?us-ascii?Q?1t/r1CpOoDnupiSu5DQ1jQm+Om7sp16NYrkkSWyoLVq3ODUaqYAiy641SZpT?=
 =?us-ascii?Q?nsaStxJxubC5lUtTyWAB4yPFShWk6vYKkNaQVCeWagtdUbHbs0f+DFXLjcgP?=
 =?us-ascii?Q?Zz/RhoLMVZcLxp8IzWgXqqMdllhkMhIuDDdIPqMrrbtLE5AYSt72pVN8WpQ0?=
 =?us-ascii?Q?74WZ9EOrK55f5E2SYVwXUXyaHwhDQecXuxx6dV2u5MlG5GyGykB2AnSmAqag?=
 =?us-ascii?Q?K5nDbaJ2nK37kLd8h6bnYUCzPXSdJ4iQYM+2nFsr?=
X-OriginatorOrg: Nvidia.com
X-MS-Exchange-CrossTenant-Network-Message-Id: 64840a70-37e5-4049-32d7-08db3baa9445
X-MS-Exchange-CrossTenant-AuthSource: LV2PR12MB5869.namprd12.prod.outlook.com
X-MS-Exchange-CrossTenant-AuthAs: Internal
X-MS-Exchange-CrossTenant-OriginalArrivalTime: 12 Apr 2023 23:06:42.3982
 (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: v8zrATfqnvyPV20/aGZNsg8RJSnBYHEQlpdAUO0kr3ISgDKfwle6uo2JrEGT25MK
X-MS-Exchange-Transport-CrossTenantHeadersStamped: DM6PR12MB4236
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>
> Reviewed-by: Shiraz Saleem <shiraz.saleem@intel.com>
> ---
> 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(-)

Applied to for-next

Thanks,
Jason