linux-kernel - Re: [PATCH RESEND 2/7] scsi: storvsc: Size the queue depth based on the ringbuffer size

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Message-ID: <CAHdzE-891eczDgPM98ihzer97Y21wX1+AsqN121y5u1yNTxmGg@mail.gmail.com>
Date:	Mon, 23 Mar 2015 17:23:00 -0700
From:	Venkatesh Srinivas <venkateshs@...gle.com>
To:	"K. Y. Srinivasan" <kys@...rosoft.com>
Cc:	gregkh@...uxfoundation.org,
	Linux Kernel Developers List <linux-kernel@...r.kernel.org>,
	devel@...uxdriverproject.org, ohering@...e.com,
	"James E.J. Bottomley" <jbottomley@...allels.com>,
	Christoph Hellwig <hch@...radead.org>,
	linux-scsi@...r.kernel.org, apw@...onical.com, vkuznets@...hat.com,
	jasowang@...hat.com
Subject: Re: [PATCH RESEND 2/7] scsi: storvsc: Size the queue depth based on
 the ringbuffer size

On Mon, Mar 23, 2015 at 2:06 PM, K. Y. Srinivasan <kys@...rosoft.com> wrote:
> Size the queue depth based on the ringbuffer size. Also accomodate for the
> fact that we could have multiple channels (ringbuffers) per adaptor.
>
> Signed-off-by: K. Y. Srinivasan <kys@...rosoft.com>
> Reviewed-by: Long Li <longli@...rosoft.com>
> ---
>  drivers/scsi/storvsc_drv.c |   27 ++++++++++++++++-----------
>  1 files changed, 16 insertions(+), 11 deletions(-)
>
> diff --git a/drivers/scsi/storvsc_drv.c b/drivers/scsi/storvsc_drv.c
> index 27fe850..5a12897 100644
> --- a/drivers/scsi/storvsc_drv.c
> +++ b/drivers/scsi/storvsc_drv.c
> @@ -309,10 +309,15 @@ enum storvsc_request_type {
>   */
>
>  static int storvsc_ringbuffer_size = (256 * PAGE_SIZE);
> +static u32 max_outstanding_req_per_channel;
> +
> +static int storvsc_vcpus_per_sub_channel = 4;
>
>  module_param(storvsc_ringbuffer_size, int, S_IRUGO);
>  MODULE_PARM_DESC(storvsc_ringbuffer_size, "Ring buffer size (bytes)");
>
> +module_param(storvsc_vcpus_per_sub_channel, int, S_IRUGO);
> +MODULE_PARM_DESC(vcpus_per_sub_channel, "Ratio of VCPUs to subchannels");
>  /*
>   * Timeout in seconds for all devices managed by this driver.
>   */
> @@ -320,7 +325,6 @@ static int storvsc_timeout = 180;
>
>  static int msft_blist_flags = BLIST_TRY_VPD_PAGES;
>
> -#define STORVSC_MAX_IO_REQUESTS                                200
>
>  static void storvsc_on_channel_callback(void *context);
>
> @@ -1376,7 +1380,6 @@ static int storvsc_do_io(struct hv_device *device,
>
>  static int storvsc_device_configure(struct scsi_device *sdevice)
>  {
> -       scsi_change_queue_depth(sdevice, STORVSC_MAX_IO_REQUESTS);
>
>         blk_queue_max_segment_size(sdevice->request_queue, PAGE_SIZE);
>
> @@ -1646,7 +1649,6 @@ static struct scsi_host_template scsi_driver = {
>         .eh_timed_out =         storvsc_eh_timed_out,
>         .slave_configure =      storvsc_device_configure,
>         .cmd_per_lun =          255,
> -       .can_queue =            STORVSC_MAX_IO_REQUESTS*STORVSC_MAX_TARGETS,
>         .this_id =              -1,
>         /* no use setting to 0 since ll_blk_rw reset it to 1 */
>         /* currently 32 */
> @@ -1686,6 +1688,7 @@ static int storvsc_probe(struct hv_device *device,
>                         const struct hv_vmbus_device_id *dev_id)
>  {
>         int ret;
> +       int num_cpus = num_online_cpus();
>         struct Scsi_Host *host;
>         struct hv_host_device *host_dev;
>         bool dev_is_ide = ((dev_id->driver_data == IDE_GUID) ? true : false);
> @@ -1694,6 +1697,7 @@ static int storvsc_probe(struct hv_device *device,
>         int max_luns_per_target;
>         int max_targets;
>         int max_channels;
> +       int max_sub_channels = 0;
>
>         /*
>          * Based on the windows host we are running on,
> @@ -1719,12 +1723,18 @@ static int storvsc_probe(struct hv_device *device,
>                 max_luns_per_target = STORVSC_MAX_LUNS_PER_TARGET;
>                 max_targets = STORVSC_MAX_TARGETS;
>                 max_channels = STORVSC_MAX_CHANNELS;
> +               /*
> +                * On Windows8 and above, we support sub-channels for storage.
> +                * The number of sub-channels offerred is based on the number of
> +                * VCPUs in the guest.
> +                */
> +               max_sub_channels = (num_cpus / storvsc_vcpus_per_sub_channel);
>                 break;
>         }
>
> -       if (dev_id->driver_data == SFC_GUID)
> -               scsi_driver.can_queue = (STORVSC_MAX_IO_REQUESTS *
> -                                        STORVSC_FC_MAX_TARGETS);
> +       scsi_driver.can_queue = (max_outstanding_req_per_channel *
> +                                max_sub_channels + 1);
> +

If num_online_cpus() returned 1 - 3, can_queue will be set to 1 I
think. Is that desired?

>         host = scsi_host_alloc(&scsi_driver,
>                                sizeof(struct hv_host_device));
>         if (!host)
> @@ -1837,7 +1847,6 @@ static struct hv_driver storvsc_drv = {
>
>  static int __init storvsc_drv_init(void)
>  {
> -       u32 max_outstanding_req_per_channel;
>
>         /*
>          * Divide the ring buffer data size (which is 1 page less
> @@ -1852,10 +1861,6 @@ static int __init storvsc_drv_init(void)
>                 vmscsi_size_delta,
>                 sizeof(u64)));
>
> -       if (max_outstanding_req_per_channel <
> -           STORVSC_MAX_IO_REQUESTS)
> -               return -EINVAL;
> -
>         return vmbus_driver_register(&storvsc_drv);
>  }

-- vs;
--
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