linux-kernel - RE: [PATCH v4] scsi: storvsc: Parameterize number hardware queues

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Date:   Tue, 2 Mar 2021 17:28:21 +0000
From:   Michael Kelley <mikelley@...rosoft.com>
To:     melanieplageman <melanieplageman@...il.com>,
        "linux-scsi@...r.kernel.org" <linux-scsi@...r.kernel.org>
CC:     "andres@...razel.de" <andres@...razel.de>,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        "jejb@...ux.ibm.com" <jejb@...ux.ibm.com>,
        KY Srinivasan <kys@...rosoft.com>,
        "linux-hyperv@...r.kernel.org" <linux-hyperv@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "martin.petersen@...cle.com" <martin.petersen@...cle.com>,
        Stephen Hemminger <sthemmin@...rosoft.com>,
        "wei.liu@...nel.org" <wei.liu@...nel.org>,
        melanieplageman <melanieplageman@...il.com>
Subject: RE: [PATCH v4] scsi: storvsc: Parameterize number hardware queues

From: Melanie Plageman (Microsoft) <melanieplageman@...il.com> Sent: Wednesday, February 24, 2021 3:30 PM
> 
> Add ability to set the number of hardware queues with new module parameter,
> storvsc_max_hw_queues. The default value remains the number of CPUs.  This
> functionality is useful in some environments (e.g. Microsoft Azure) where
> decreasing the number of hardware queues has been shown to improve
> performance.
> 
> Signed-off-by: Melanie Plageman (Microsoft) <melanieplageman@...il.com>
> ---
> Updated since v3:
> - permissions in octal
> - param type changed to unsigned int
> - removed value checking from module init function
> - simplified value checking logic in probe function
> 
>  drivers/scsi/storvsc_drv.c | 18 ++++++++++++++++--
>  1 file changed, 16 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/scsi/storvsc_drv.c b/drivers/scsi/storvsc_drv.c
> index 6bc5453cea8a..dfe005c03734 100644
> --- a/drivers/scsi/storvsc_drv.c
> +++ b/drivers/scsi/storvsc_drv.c
> @@ -366,10 +366,14 @@ static u32 max_outstanding_req_per_channel;
>  static int storvsc_change_queue_depth(struct scsi_device *sdev, int queue_depth);
> 
>  static int storvsc_vcpus_per_sub_channel = 4;
> +static unsigned int storvsc_max_hw_queues;
> 
>  module_param(storvsc_ringbuffer_size, int, S_IRUGO);
>  MODULE_PARM_DESC(storvsc_ringbuffer_size, "Ring buffer size (bytes)");
> 
> +module_param(storvsc_max_hw_queues, uint, 0644);
> +MODULE_PARM_DESC(storvsc_max_hw_queues, "Maximum number of hardware queues");
> +
>  module_param(storvsc_vcpus_per_sub_channel, int, S_IRUGO);
>  MODULE_PARM_DESC(storvsc_vcpus_per_sub_channel, "Ratio of VCPUs to
> subchannels");
> 
> @@ -1907,6 +1911,7 @@ static int storvsc_probe(struct hv_device *device,
>  {
>  	int ret;
>  	int num_cpus = num_online_cpus();
> +	int num_present_cpus = num_present_cpus();
>  	struct Scsi_Host *host;
>  	struct hv_host_device *host_dev;
>  	bool dev_is_ide = ((dev_id->driver_data == IDE_GUID) ? true : false);
> @@ -2015,8 +2020,17 @@ static int storvsc_probe(struct hv_device *device,
>  	 * For non-IDE disks, the host supports multiple channels.
>  	 * Set the number of HW queues we are supporting.
>  	 */
> -	if (!dev_is_ide)
> -		host->nr_hw_queues = num_present_cpus();
> +	if (!dev_is_ide) {
> +		if (storvsc_max_hw_queues > num_present_cpus) {
> +			storvsc_max_hw_queues = 0;
> +			storvsc_log(device, STORVSC_LOGGING_WARN,
> +				"Resetting invalid storvsc_max_hw_queues value to default.\n");
> +		}
> +		if (storvsc_max_hw_queues)
> +			host->nr_hw_queues = storvsc_max_hw_queues;
> +		else
> +			host->nr_hw_queues = num_present_cpus;
> +	}
> 
>  	/*
>  	 * Set the error handler work queue.
> --
> 2.20.1

Reviewed-by: Michael Kelley <mikelley@...rosoft.com>