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Tsirkin" CC: Stefan Hajnoczi , , , , , , , , References: <20210831135035.6443-1-mgurtovoy@nvidia.com> <20210905120234-mutt-send-email-mst@kernel.org> <98309fcd-3abe-1f27-fe52-e8fcc58bec13@nvidia.com> <20210906071957-mutt-send-email-mst@kernel.org> <1cbbe6e2-1473-8696-565c-518fc1016a1a@nvidia.com> <20210909094001-mutt-send-email-mst@kernel.org> <456e1704-67e9-aac9-a82a-44fed65dd153@nvidia.com> <20210909114029-mutt-send-email-mst@kernel.org> From: Max Gurtovoy Message-ID: Date: Thu, 9 Sep 2021 18:51:56 +0300 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.14.0 MIME-Version: 1.0 In-Reply-To: <20210909114029-mutt-send-email-mst@kernel.org> Content-Type: text/plain; charset="utf-8"; format=flowed Content-Transfer-Encoding: 7bit Content-Language: en-US X-Originating-IP: [172.20.187.5] X-ClientProxiedBy: HQMAIL111.nvidia.com (172.20.187.18) To DRHQMAIL107.nvidia.com (10.27.9.16) X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-Office365-Filtering-Correlation-Id: 3c84d703-05e0-4f89-732c-08d973a9c423 X-MS-TrafficTypeDiagnostic: DM6PR12MB5535: X-Microsoft-Antispam-PRVS: X-MS-Oob-TLC-OOBClassifiers: OLM:8273; X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0; X-Microsoft-Antispam-Message-Info: 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 X-Forefront-Antispam-Report: CIP:216.228.112.36;CTRY:US;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:mail.nvidia.com;PTR:schybrid05.nvidia.com;CAT:NONE;SFS:(4636009)(36840700001)(46966006)(8936002)(54906003)(316002)(8676002)(356005)(2906002)(16576012)(36906005)(7636003)(53546011)(16526019)(6666004)(26005)(86362001)(36860700001)(82310400003)(186003)(31686004)(70586007)(508600001)(5660300002)(70206006)(426003)(2616005)(6916009)(4326008)(31696002)(47076005)(336012)(36756003)(83380400001)(43740500002);DIR:OUT;SFP:1101; X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 09 Sep 2021 15:52:02.5881 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 3c84d703-05e0-4f89-732c-08d973a9c423 X-MS-Exchange-CrossTenant-Id: 43083d15-7273-40c1-b7db-39efd9ccc17a X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=43083d15-7273-40c1-b7db-39efd9ccc17a;Ip=[216.228.112.36];Helo=[mail.nvidia.com] X-MS-Exchange-CrossTenant-AuthSource: CO1NAM11FT017.eop-nam11.prod.protection.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: DM6PR12MB5535 Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On 9/9/2021 6:40 PM, Michael S. Tsirkin wrote: > On Thu, Sep 09, 2021 at 06:37:37PM +0300, Max Gurtovoy wrote: >> On 9/9/2021 4:42 PM, Michael S. Tsirkin wrote: >>> On Mon, Sep 06, 2021 at 02:59:40PM +0300, Max Gurtovoy wrote: >>>> On 9/6/2021 2:20 PM, Michael S. Tsirkin wrote: >>>>> On Mon, Sep 06, 2021 at 01:31:32AM +0300, Max Gurtovoy wrote: >>>>>> On 9/5/2021 7:02 PM, Michael S. Tsirkin wrote: >>>>>>> On Thu, Sep 02, 2021 at 02:45:52PM +0100, Stefan Hajnoczi wrote: >>>>>>>> On Tue, Aug 31, 2021 at 04:50:35PM +0300, Max Gurtovoy wrote: >>>>>>>>> Sometimes a user would like to control the amount of IO queues to be >>>>>>>>> created for a block device. For example, for limiting the memory >>>>>>>>> footprint of virtio-blk devices. >>>>>>>>> >>>>>>>>> Signed-off-by: Max Gurtovoy >>>>>>>>> --- >>>>>>>>> >>>>>>>>> changes from v1: >>>>>>>>> - use param_set_uint_minmax (from Christoph) >>>>>>>>> - added "Should > 0" to module description >>>>>>>>> >>>>>>>>> Note: This commit apply on top of Jens's branch for-5.15/drivers >>>>>>>>> --- >>>>>>>>> drivers/block/virtio_blk.c | 20 +++++++++++++++++++- >>>>>>>>> 1 file changed, 19 insertions(+), 1 deletion(-) >>>>>>>>> >>>>>>>>> diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c >>>>>>>>> index 4b49df2dfd23..9332fc4e9b31 100644 >>>>>>>>> --- a/drivers/block/virtio_blk.c >>>>>>>>> +++ b/drivers/block/virtio_blk.c >>>>>>>>> @@ -24,6 +24,22 @@ >>>>>>>>> /* The maximum number of sg elements that fit into a virtqueue */ >>>>>>>>> #define VIRTIO_BLK_MAX_SG_ELEMS 32768 >>>>>>>>> +static int virtblk_queue_count_set(const char *val, >>>>>>>>> + const struct kernel_param *kp) >>>>>>>>> +{ >>>>>>>>> + return param_set_uint_minmax(val, kp, 1, nr_cpu_ids); >>>>>>>>> +} >>>>> Hmm which tree is this for? >>>> I've mentioned in the note that it apply on branch for-5.15/drivers. But now >>>> you can apply it on linus/master as well. >>>> >>>> >>>>>>>>> + >>>>>>>>> +static const struct kernel_param_ops queue_count_ops = { >>>>>>>>> + .set = virtblk_queue_count_set, >>>>>>>>> + .get = param_get_uint, >>>>>>>>> +}; >>>>>>>>> + >>>>>>>>> +static unsigned int num_io_queues; >>>>>>>>> +module_param_cb(num_io_queues, &queue_count_ops, &num_io_queues, 0644); >>>>>>>>> +MODULE_PARM_DESC(num_io_queues, >>>>>>>>> + "Number of IO virt queues to use for blk device. Should > 0"); >>>>> better: >>>>> >>>>> +MODULE_PARM_DESC(num_io_request_queues, >>>>> + "Limit number of IO request virt queues to use for each device. 0 for now limit"); >>>> You proposed it and I replied on it bellow. >>> Can't say I understand 100% what you are saying. Want to send >>> a description that does make sense to you but >>> also reflects reality? 0 is the default so >>> "should > 0" besides being ungrammatical does not seem t" >>> reflect what it does ... >> if you "modprobe virtio_blk" the previous behavior will happen. >> >> You can't "modprobe virtio_blk num_io_request_queues=0" since the minimal >> value is 1. >> >> So your description is not reflecting the code. >> >> We can do: >> >> MODULE_PARM_DESC(num_io_request_queues, "Number of request virt queues to use for blk device. Minimum value is 1 queue"); > What's the default value? We should document that. default value for static global variables is 0. MODULE_PARM_DESC(num_io_request_queues, "Number of request virt queues to use for blk device. Minimum value is 1 queue. Default and Maximum value is equal to the total number of CPUs"); > >>>>>>>>> + >>>>>>>>> static int major; >>>>>>>>> static DEFINE_IDA(vd_index_ida); >>>>>>>>> @@ -501,7 +517,9 @@ static int init_vq(struct virtio_blk *vblk) >>>>>>>>> if (err) >>>>>>>>> num_vqs = 1; >>>>>>>>> - num_vqs = min_t(unsigned int, nr_cpu_ids, num_vqs); >>>>>>>>> + num_vqs = min_t(unsigned int, >>>>>>>>> + min_not_zero(num_io_queues, nr_cpu_ids), >>>>>>>>> + num_vqs); >>>>>>>> If you respin, please consider calling them request queues. That's the >>>>>>>> terminology from the VIRTIO spec and it's nice to keep it consistent. >>>>>>>> But the purpose of num_io_queues is clear, so: >>>>>>>> >>>>>>>> Reviewed-by: Stefan Hajnoczi >>>>>>> I did this: >>>>>>> +static unsigned int num_io_request_queues; >>>>>>> +module_param_cb(num_io_request_queues, &queue_count_ops, &num_io_request_queues, 0644); >>>>>>> +MODULE_PARM_DESC(num_io_request_queues, >>>>>>> + "Limit number of IO request virt queues to use for each device. 0 for now limit"); >>>>>> The parameter is writable and can be changed and then new devices might be >>>>>> probed with new value. >>>>>> >>>>>> It can't be zero in the code. we can change param_set_uint_minmax args and >>>>>> say that 0 says nr_cpus. >>>>>> >>>>>> I'm ok with the renaming but I prefer to stick to the description we gave in >>>>>> V3 of this patch (and maybe enable value of 0 as mentioned above).