Message-ID: <ee7c8d05-93bf-3cc8-781f-2d6302778b3f@nvidia.com>
Date:   Mon, 15 Nov 2021 14:57:58 +0200
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101
 Thunderbird/91.2.0
Subject: Re: [PATCH] net: bridge: Slightly optimize 'find_portno()'
Content-Language: en-US
To:     Christophe JAILLET <christophe.jaillet@wanadoo.fr>,
        roopa@nvidia.com, davem@davemloft.net, kuba@kernel.org
Cc:     bridge@lists.linux-foundation.org, netdev@vger.kernel.org,
        linux-kernel@vger.kernel.org, kernel-janitors@vger.kernel.org
References: <00c39d09c8df7ad0673bf2043f6566d6ef08b789.1636916479.git.christophe.jaillet@wanadoo.fr>
From:   Nikolay Aleksandrov <nikolay@nvidia.com>
In-Reply-To: <00c39d09c8df7ad0673bf2043f6566d6ef08b789.1636916479.git.christophe.jaillet@wanadoo.fr>
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 7bit
MIME-Version: 1.0
X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1
X-MS-Exchange-AntiSpam-MessageData-0: =?utf-8?B?clFqRkthMjdrOC9xY21iNTYzbWJ6d3pRbVprZFpZYzJGK0dTOXRZNVpBR2Vn?=
 =?utf-8?B?Y0ZSWW5OVzVxOUdJZVk3d3pjSmU4S1psOHozMDhyZ1FVUHFSVWxPOE4vS0I1?=
 =?utf-8?B?dlF4V3FjVFBoYVhOaE1ycXV5RlBmZGdvZjNiTm1uMUlOeDFQMzA0NmlsSXNn?=
 =?utf-8?B?RVFuRjR0enpGZXEvQXZFQjZqeDhIcHMrWjlHdmZjQ1d0WkRXakpPSUZwdTdD?=
 =?utf-8?B?L1hTNXEvZDl0d0tTakl5RCtmK0ZVcENTZmdIalBTUFBXMm40NHozM2JGSFQ3?=
 =?utf-8?B?SE1IeGNyR0d2KzBVNG5MRzhjTTJPMVJHOWZKdXQ4WVdJQ0hmOWg2OHRWR2J5?=
 =?utf-8?B?eWpJdDZrM2JNdnA1aWlTYVRBd21OVEJ1eTlRbmpEVEIxaWVFc1FyVUx4NnJ6?=
 =?utf-8?B?cWI4MUdsM2F3cUNWd0xaZnJzd21pbTlnMzNNTllRU3IxaFJaWEdGMlBrcld6?=
 =?utf-8?B?MkJUT0p1aWc3MlBlMWlTZCs5SVRUREVBS29qK0NMK1NOdjhiZnAxS0dzVEsv?=
 =?utf-8?B?amFmNTZKUHM2SFhweDVCeEM2ek8vdGZVclk2L3NnOUlBZVB1b3pBelVoUGEy?=
 =?utf-8?B?UDZBVkExOEduUStRazdXK21WUGVjZ0xZK24rdjNiWDY4WjVuaSswVVZFSGdX?=
 =?utf-8?B?OUJXUlFhbzZLeTUzR2o0N2RsMVZ6anBvZTJJVkNBZTV2ZzFUQ01ReWRaRUVv?=
 =?utf-8?B?ZlhHcVFJNGtJR256RDIvbWxMTG9vN1MyQmdBeEFPQWlEazlhUXp2VHRFOHdW?=
 =?utf-8?B?bnVCdWRJTVJVMDFjTEhFd0gvV01IV1ZGbVZxaUYyV0dBaTNmanRPaEMxUEkw?=
 =?utf-8?B?cmlHR1RIVzRXR05hL2ZGbCs3TVBlVDY2ODVNdHdjMUM0R2p6VDFwdmtWTkQ4?=
 =?utf-8?B?ZWhlS0lTQlVaeWRHRytMUnU0NEdFNEcrMHVyanNBUng4ZGtUekJBTGs2Zm1t?=
 =?utf-8?B?Sk5lWmdwZEVQdjZQTjBMSWRMV1FIdUI3L3k2VWgzMHVwaWtzSFlvK3U5VlJD?=
 =?utf-8?B?VGYvVWlxditJNHJaQUtKdWY2T0NOL1NvY1pzU0NBSlN6cm1jME1DUlZpV1hl?=
 =?utf-8?B?SVRmNGFuRkRJYXN2bERZNnJkalNBbUFFSmRYei9hOXhaK0JtdWdQNUVlOXhX?=
 =?utf-8?B?U091NEVIbWg4SFJ4N1Q0TTZDd0pKUDFwbWxRa0ZNaUEwSi9KOEcvaVNVejNU?=
 =?utf-8?B?T082c3FCNGNSN0VMMnNqOXJjR01IOEsxdkY4ODFnQW8rSHBtbWVteFdhVTR2?=
 =?utf-8?B?bllEUGhaY2lFWHlzTjJuajc0eUVtTDh3dE9adGtWVU5NUzNIdmNIaXZacUw0?=
 =?utf-8?B?eEFtQldRM3pGUHRIQ1cwdWtwbzhYa1RiOE9ka1BLdTdJZk9DMndiNHY3aWpD?=
 =?utf-8?B?NzRkUHdLdkdRQ3pUdDE5MkYwMzRMVXMxV0NpVHRTNHlMMkY0elFGenNCdmsy?=
 =?utf-8?B?QVMxTkxWeTRCcnIxN2dOSlJWTnJKZFlHNVJ1YXlsTExFMWxGOUVGcDk2cTZX?=
 =?utf-8?B?NlBQVnhwa2xVMTdMRkM3N3l4bm1hUlB2TzdoTUI1YmJxb1lWT2h4RnNEUkxQ?=
 =?utf-8?B?TW1GL3JDOGo0Uy8xVHhKcVYxbXYyRDJQMkNJbEFMakF1QnRlQ2ZFVW1iVUtx?=
 =?utf-8?B?dk9sZFBWSDlKcE16cUFnWEhJVWp2QUI0UzhTSHlxR0ErZ00wY3lqTlk2TFh5?=
 =?utf-8?B?T3ljNXlsWVh2RWpaanpLTXNVT244bkxxUjZiaFVaVytzV29lbWdBdlFqam5z?=
 =?utf-8?B?di9IbURUTGZwNEgvV2tFYjJZWjdzd3pjei9vM1pFc2NLb3E2UFhpaWs3eGFj?=
 =?utf-8?B?eElrODdnYzdWVm5BQjRLNDZmR00vUURQNGRXWFZpWURUL3doZ05XWkp5NFEy?=
 =?utf-8?B?WFpMaWFSWHZOUE8zckgvaEtndGZ6N25ZaHd1czhpWjROaGUzRkNGUlo3M0hx?=
 =?utf-8?B?Q2psajkwamZodVkySW5wQ2l2MmMrMnJYeVljR2xGT2duVEYzeVNGbHh3dlhO?=
 =?utf-8?B?ZWNrMVlvRk11Zm5vMjE2WnpSeWhOa0J4MjlvWS9uaFZlaGg2bE5WdExoMWNK?=
 =?utf-8?B?aHZXendoMHFMTVFvb2hQTENhVGlCTDJ2YU4rNHJKQ1hoTUhJT1ZDUWRKeGJ0?=
 =?utf-8?B?SkxKMmFVbm1QU1I0Um1aRmFoeVBJSHZiYjhvd0dpYURPK1dqUEVFWncvNDkr?=
 =?utf-8?Q?Lg4nwNWFoY6yoCGGc0MH5yQ=3D?=
X-OriginatorOrg: Nvidia.com
X-MS-Exchange-CrossTenant-Network-Message-Id: 6fa9c7eb-76c6-4142-9b79-08d9a837908f
X-MS-Exchange-CrossTenant-AuthSource: DM4PR12MB5278.namprd12.prod.outlook.com
X-MS-Exchange-CrossTenant-AuthAs: Internal
X-MS-Exchange-CrossTenant-OriginalArrivalTime: 15 Nov 2021 12:58:05.6104
 (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: 8t1rmFU0K14aAmXpX4f06CDB1N6ER4YpF3IUHVCDPWaWubxSE8KTngqPhqpc+/2XlkL88swMb06kH4T9dqufrQ==
X-MS-Exchange-Transport-CrossTenantHeadersStamped: DM6PR12MB5568
Precedence: bulk
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

On 14/11/2021 21:02, Christophe JAILLET wrote:
> The 'inuse' bitmap is local to this function. So we can use the
> non-atomic '__set_bit()' to save a few cycles.
> 
> While at it, also remove some useless {}.
> 
> Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
> ---
>  net/bridge/br_if.c | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/net/bridge/br_if.c b/net/bridge/br_if.c
> index c1183fef1f21..64b2d4fb50f5 100644
> --- a/net/bridge/br_if.c
> +++ b/net/bridge/br_if.c
> @@ -397,10 +397,10 @@ static int find_portno(struct net_bridge *br)
>  	if (!inuse)
>  		return -ENOMEM;
>  
> -	set_bit(0, inuse);	/* zero is reserved */
> -	list_for_each_entry(p, &br->port_list, list) {
> -		set_bit(p->port_no, inuse);
> -	}
> +	__set_bit(0, inuse);	/* zero is reserved */
> +	list_for_each_entry(p, &br->port_list, list)
> +		__set_bit(p->port_no, inuse);
> +
>  	index = find_first_zero_bit(inuse, BR_MAX_PORTS);
>  	bitmap_free(inuse);
>  
> 

This should be targeted at net-next.
The patch itself looks ok, TBH it's a slow path so speed
doesn't really matter but it's a straight-forward change.

Acked-by: Nikolay Aleksandrov <nikolay@nvidia.com>