Re: [PATCH 2/2] dmaengine: idxd: add support for configurable max wq batch size

[Vinod Koul <vkoul@kernel.org>]

On 25-08-20, 13:25, Dave Jiang wrote:
> Add sysfs attribute max_batch_size to wq in order to allow the max batch
> size configured on a per wq basis. Add support code to configure
> the valid user input on wq enable. This is a performance tuning
> parameter.
> 
> Signed-off-by: Dave Jiang <dave.jiang@intel.com>
> ---
>  drivers/dma/idxd/device.c |    2 +-
>  drivers/dma/idxd/idxd.h   |    1 +
>  drivers/dma/idxd/init.c   |    1 +
>  drivers/dma/idxd/sysfs.c  |   38 ++++++++++++++++++++++++++++++++++++++
>  4 files changed, 41 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/dma/idxd/device.c b/drivers/dma/idxd/device.c
> index b8dbb7001933..00dab1465ca3 100644
> --- a/drivers/dma/idxd/device.c
> +++ b/drivers/dma/idxd/device.c
> @@ -530,7 +530,7 @@ static int idxd_wq_config_write(struct idxd_wq *wq)
>  
>  	/* bytes 12-15 */
>  	wq->wqcfg.max_xfer_shift = ilog2(wq->max_xfer_bytes);
> -	wq->wqcfg.max_batch_shift = idxd->hw.gen_cap.max_batch_shift;
> +	wq->wqcfg.max_batch_shift = ilog2(wq->max_batch_size);
>  
>  	dev_dbg(dev, "WQ %d CFGs\n", wq->id);
>  	for (i = 0; i < 8; i++) {
> diff --git a/drivers/dma/idxd/idxd.h b/drivers/dma/idxd/idxd.h
> index 81db2a472822..e8bec6eb9f7e 100644
> --- a/drivers/dma/idxd/idxd.h
> +++ b/drivers/dma/idxd/idxd.h
> @@ -115,6 +115,7 @@ struct idxd_wq {
>  	struct dma_chan dma_chan;
>  	char name[WQ_NAME_SIZE + 1];
>  	u64 max_xfer_bytes;
> +	u32 max_batch_size;
>  };
>  
>  struct idxd_engine {
> diff --git a/drivers/dma/idxd/init.c b/drivers/dma/idxd/init.c
> index e5ed5750a6d0..11e5ce168177 100644
> --- a/drivers/dma/idxd/init.c
> +++ b/drivers/dma/idxd/init.c
> @@ -177,6 +177,7 @@ static int idxd_setup_internals(struct idxd_device *idxd)
>  		mutex_init(&wq->wq_lock);
>  		wq->idxd_cdev.minor = -1;
>  		wq->max_xfer_bytes = idxd->max_xfer_bytes;
> +		wq->max_batch_size = idxd->max_batch_size;
>  	}
>  
>  	for (i = 0; i < idxd->max_engines; i++) {
> diff --git a/drivers/dma/idxd/sysfs.c b/drivers/dma/idxd/sysfs.c
> index 26b3ace66782..c5f19802cb9e 100644
> --- a/drivers/dma/idxd/sysfs.c
> +++ b/drivers/dma/idxd/sysfs.c
> @@ -1103,6 +1103,43 @@ static struct device_attribute dev_attr_wq_max_transfer_size =
>  		__ATTR(max_transfer_size, 0644,
>  		       wq_max_transfer_size_show, wq_max_transfer_size_store);
>  
> +static ssize_t wq_max_batch_size_show(struct device *dev, struct device_attribute *attr, char *buf)
> +{
> +	struct idxd_wq *wq = container_of(dev, struct idxd_wq, conf_dev);
> +
> +	return sprintf(buf, "%u\n", wq->max_batch_size);
> +}
> +
> +static ssize_t wq_max_batch_size_store(struct device *dev, struct device_attribute *attr,
> +				       const char *buf, size_t count)
> +{
> +	struct idxd_wq *wq = container_of(dev, struct idxd_wq, conf_dev);
> +	struct idxd_device *idxd = wq->idxd;
> +	u32 batch_size;
> +	int rc;
> +
> +	if (wq->state != IDXD_WQ_DISABLED)
> +		return -EPERM;
> +
> +	rc = kstrtou32(buf, 10, &batch_size);
> +	if (rc < 0)
> +		return -EINVAL;
> +
> +	if (batch_size == 0)
> +		return -EINVAL;

seems quite similar to previous patch, maybe a helper to get the value?

> +
> +	batch_size = roundup_pow_of_two(batch_size);
> +	if (batch_size > idxd->max_batch_size)
> +		return -EINVAL;
> +
> +	wq->max_batch_size = batch_size;
> +
> +	return count;
> +}
> +
> +static struct device_attribute dev_attr_wq_max_batch_size =
> +		__ATTR(max_batch_size, 0644, wq_max_batch_size_show, wq_max_batch_size_store);
> +
>  static struct attribute *idxd_wq_attributes[] = {
>  	&dev_attr_wq_clients.attr,
>  	&dev_attr_wq_state.attr,
> @@ -1114,6 +1151,7 @@ static struct attribute *idxd_wq_attributes[] = {
>  	&dev_attr_wq_name.attr,
>  	&dev_attr_wq_cdev_minor.attr,
>  	&dev_attr_wq_max_transfer_size.attr,
> +	&dev_attr_wq_max_batch_size.attr,

ABI?

>  	NULL,
>  };
>  

-- 
~Vinod