LinuxTV Patchwork [v6,2/2] media: usb: pwc: Don't use coherent DMA buffers for ISO transfer

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Submitter Matwey V. Kornilov
Date Nov. 9, 2018, 7:03 p.m.
Message ID <20181109190327.23606-3-matwey@sai.msu.ru>
Download mbox | patch
Permalink /patch/52882/
State Under Review
Delegated to: Hans Verkuil
Headers show

Comments

Matwey V. Kornilov - Nov. 9, 2018, 7:03 p.m.
DMA cocherency slows the transfer down on systems without hardware
coherent DMA.
Instead we use noncocherent DMA memory and explicit sync at data receive
handler.

Based on previous commit the following performance benchmarks have been
carried out. Average memcpy() data transfer rate (rate) and handler
completion time (time) have been measured when running video stream at
640x480 resolution at 10fps.

x86_64 based system (Intel Core i5-3470). This platform has hardware
coherent DMA support and proposed change doesn't make big difference here.

 * kmalloc:            rate = (2.0 +- 0.4) GBps
                       time = (5.0 +- 3.0) usec
 * usb_alloc_coherent: rate = (3.4 +- 1.2) GBps
                       time = (3.5 +- 3.0) usec

We see that the measurements agree within error ranges in this case.
So theoretically predicted performance downgrade cannot be reliably
measured here.

armv7l based system (TI AM335x BeagleBone Black @ 300MHz). This platform
has no hardware coherent DMA support. DMA coherence is implemented via
disabled page caching that slows down memcpy() due to memory controller
behaviour.

 * kmalloc:            rate =  ( 94 +- 4) MBps
                       time =  (101 +- 4) usec
 * usb_alloc_coherent: rate = (28.1 +- 0.1) MBps
                       time =  (341 +- 2) usec

Note, that quantative difference leads (this commit leads to 3.3 times
acceleration) to qualitative behavior change in this case. As it was
stated before, the video stream cannot be successfully received at AM335x
platforms with MUSB based USB host controller due to performance issues
[1].

[1] https://www.spinics.net/lists/linux-usb/msg165735.html

Signed-off-by: Matwey V. Kornilov <matwey@sai.msu.ru>
---
 drivers/media/usb/pwc/pwc-if.c | 62 +++++++++++++++++++++++++++++++++---------
 1 file changed, 49 insertions(+), 13 deletions(-)
Matwey V. Kornilov - Nov. 21, 2018, 6:15 p.m.
??, 9 ????. 2018 ?. ? 22:03, Matwey V. Kornilov <matwey@sai.msu.ru>:
>
> DMA cocherency slows the transfer down on systems without hardware
> coherent DMA.
> Instead we use noncocherent DMA memory and explicit sync at data receive
> handler.
>
> Based on previous commit the following performance benchmarks have been
> carried out. Average memcpy() data transfer rate (rate) and handler
> completion time (time) have been measured when running video stream at
> 640x480 resolution at 10fps.
>
> x86_64 based system (Intel Core i5-3470). This platform has hardware
> coherent DMA support and proposed change doesn't make big difference here.
>
>  * kmalloc:            rate = (2.0 +- 0.4) GBps
>                        time = (5.0 +- 3.0) usec
>  * usb_alloc_coherent: rate = (3.4 +- 1.2) GBps
>                        time = (3.5 +- 3.0) usec
>
> We see that the measurements agree within error ranges in this case.
> So theoretically predicted performance downgrade cannot be reliably
> measured here.
>
> armv7l based system (TI AM335x BeagleBone Black @ 300MHz). This platform
> has no hardware coherent DMA support. DMA coherence is implemented via
> disabled page caching that slows down memcpy() due to memory controller
> behaviour.
>
>  * kmalloc:            rate =  ( 94 +- 4) MBps
>                        time =  (101 +- 4) usec
>  * usb_alloc_coherent: rate = (28.1 +- 0.1) MBps
>                        time =  (341 +- 2) usec
>
> Note, that quantative difference leads (this commit leads to 3.3 times
> acceleration) to qualitative behavior change in this case. As it was
> stated before, the video stream cannot be successfully received at AM335x
> platforms with MUSB based USB host controller due to performance issues
> [1].
>
> [1] https://www.spinics.net/lists/linux-usb/msg165735.html
>
> Signed-off-by: Matwey V. Kornilov <matwey@sai.msu.ru>

Ping

> ---
>  drivers/media/usb/pwc/pwc-if.c | 62 +++++++++++++++++++++++++++++++++---------
>  1 file changed, 49 insertions(+), 13 deletions(-)
>
> diff --git a/drivers/media/usb/pwc/pwc-if.c b/drivers/media/usb/pwc/pwc-if.c
> index 53c111bd5a22..a81fb319b339 100644
> --- a/drivers/media/usb/pwc/pwc-if.c
> +++ b/drivers/media/usb/pwc/pwc-if.c
> @@ -159,6 +159,32 @@ static const struct video_device pwc_template = {
>  /***************************************************************************/
>  /* Private functions */
>
> +static void *pwc_alloc_urb_buffer(struct device *dev,
> +                                 size_t size, dma_addr_t *dma_handle)
> +{
> +       void *buffer = kmalloc(size, GFP_KERNEL);
> +
> +       if (!buffer)
> +               return NULL;
> +
> +       *dma_handle = dma_map_single(dev, buffer, size, DMA_FROM_DEVICE);
> +       if (dma_mapping_error(dev, *dma_handle)) {
> +               kfree(buffer);
> +               return NULL;
> +       }
> +
> +       return buffer;
> +}
> +
> +static void pwc_free_urb_buffer(struct device *dev,
> +                               size_t size,
> +                               void *buffer,
> +                               dma_addr_t dma_handle)
> +{
> +       dma_unmap_single(dev, dma_handle, size, DMA_FROM_DEVICE);
> +       kfree(buffer);
> +}
> +
>  static struct pwc_frame_buf *pwc_get_next_fill_buf(struct pwc_device *pdev)
>  {
>         unsigned long flags = 0;
> @@ -306,6 +332,11 @@ static void pwc_isoc_handler(struct urb *urb)
>         /* Reset ISOC error counter. We did get here, after all. */
>         pdev->visoc_errors = 0;
>
> +       dma_sync_single_for_cpu(&urb->dev->dev,
> +                               urb->transfer_dma,
> +                               urb->transfer_buffer_length,
> +                               DMA_FROM_DEVICE);
> +
>         /* vsync: 0 = don't copy data
>                   1 = sync-hunt
>                   2 = synched
> @@ -352,6 +383,11 @@ static void pwc_isoc_handler(struct urb *urb)
>                 pdev->vlast_packet_size = flen;
>         }
>
> +       dma_sync_single_for_device(&urb->dev->dev,
> +                                  urb->transfer_dma,
> +                                  urb->transfer_buffer_length,
> +                                  DMA_FROM_DEVICE);
> +
>  handler_end:
>         trace_pwc_handler_exit(urb, pdev);
>
> @@ -428,16 +464,15 @@ static int pwc_isoc_init(struct pwc_device *pdev)
>                 urb->dev = udev;
>                 urb->pipe = usb_rcvisocpipe(udev, pdev->vendpoint);
>                 urb->transfer_flags = URB_ISO_ASAP | URB_NO_TRANSFER_DMA_MAP;
> -               urb->transfer_buffer = usb_alloc_coherent(udev,
> -                                                         ISO_BUFFER_SIZE,
> -                                                         GFP_KERNEL,
> -                                                         &urb->transfer_dma);
> +               urb->transfer_buffer_length = ISO_BUFFER_SIZE;
> +               urb->transfer_buffer = pwc_alloc_urb_buffer(&udev->dev,
> +                                                           urb->transfer_buffer_length,
> +                                                           &urb->transfer_dma);
>                 if (urb->transfer_buffer == NULL) {
>                         PWC_ERROR("Failed to allocate urb buffer %d\n", i);
>                         pwc_isoc_cleanup(pdev);
>                         return -ENOMEM;
>                 }
> -               urb->transfer_buffer_length = ISO_BUFFER_SIZE;
>                 urb->complete = pwc_isoc_handler;
>                 urb->context = pdev;
>                 urb->start_frame = 0;
> @@ -488,15 +523,16 @@ static void pwc_iso_free(struct pwc_device *pdev)
>
>         /* Freeing ISOC buffers one by one */
>         for (i = 0; i < MAX_ISO_BUFS; i++) {
> -               if (pdev->urbs[i]) {
> +               struct urb *urb = pdev->urbs[i];
> +
> +               if (urb) {
>                         PWC_DEBUG_MEMORY("Freeing URB\n");
> -                       if (pdev->urbs[i]->transfer_buffer) {
> -                               usb_free_coherent(pdev->udev,
> -                                       pdev->urbs[i]->transfer_buffer_length,
> -                                       pdev->urbs[i]->transfer_buffer,
> -                                       pdev->urbs[i]->transfer_dma);
> -                       }
> -                       usb_free_urb(pdev->urbs[i]);
> +                       if (urb->transfer_buffer)
> +                               pwc_free_urb_buffer(&urb->dev->dev,
> +                                                   urb->transfer_buffer_length,
> +                                                   urb->transfer_buffer,
> +                                                   urb->transfer_dma);
> +                       usb_free_urb(urb);
>                         pdev->urbs[i] = NULL;
>                 }
>         }
> --
> 2.16.4
>
Matwey V. Kornilov - Nov. 30, 2018, 12:20 p.m.
??, 21 ????. 2018 ?. ? 21:15, Matwey V. Kornilov <matwey.kornilov@gmail.com>:
>
> ??, 9 ????. 2018 ?. ? 22:03, Matwey V. Kornilov <matwey@sai.msu.ru>:
> >
> > DMA cocherency slows the transfer down on systems without hardware
> > coherent DMA.
> > Instead we use noncocherent DMA memory and explicit sync at data receive
> > handler.
> >
> > Based on previous commit the following performance benchmarks have been
> > carried out. Average memcpy() data transfer rate (rate) and handler
> > completion time (time) have been measured when running video stream at
> > 640x480 resolution at 10fps.
> >
> > x86_64 based system (Intel Core i5-3470). This platform has hardware
> > coherent DMA support and proposed change doesn't make big difference here.
> >
> >  * kmalloc:            rate = (2.0 +- 0.4) GBps
> >                        time = (5.0 +- 3.0) usec
> >  * usb_alloc_coherent: rate = (3.4 +- 1.2) GBps
> >                        time = (3.5 +- 3.0) usec
> >
> > We see that the measurements agree within error ranges in this case.
> > So theoretically predicted performance downgrade cannot be reliably
> > measured here.
> >
> > armv7l based system (TI AM335x BeagleBone Black @ 300MHz). This platform
> > has no hardware coherent DMA support. DMA coherence is implemented via
> > disabled page caching that slows down memcpy() due to memory controller
> > behaviour.
> >
> >  * kmalloc:            rate =  ( 94 +- 4) MBps
> >                        time =  (101 +- 4) usec
> >  * usb_alloc_coherent: rate = (28.1 +- 0.1) MBps
> >                        time =  (341 +- 2) usec
> >
> > Note, that quantative difference leads (this commit leads to 3.3 times
> > acceleration) to qualitative behavior change in this case. As it was
> > stated before, the video stream cannot be successfully received at AM335x
> > platforms with MUSB based USB host controller due to performance issues
> > [1].
> >
> > [1] https://www.spinics.net/lists/linux-usb/msg165735.html
> >
> > Signed-off-by: Matwey V. Kornilov <matwey@sai.msu.ru>
>
> Ping

Ping

>
> > ---
> >  drivers/media/usb/pwc/pwc-if.c | 62 +++++++++++++++++++++++++++++++++---------
> >  1 file changed, 49 insertions(+), 13 deletions(-)
> >
> > diff --git a/drivers/media/usb/pwc/pwc-if.c b/drivers/media/usb/pwc/pwc-if.c
> > index 53c111bd5a22..a81fb319b339 100644
> > --- a/drivers/media/usb/pwc/pwc-if.c
> > +++ b/drivers/media/usb/pwc/pwc-if.c
> > @@ -159,6 +159,32 @@ static const struct video_device pwc_template = {
> >  /***************************************************************************/
> >  /* Private functions */
> >
> > +static void *pwc_alloc_urb_buffer(struct device *dev,
> > +                                 size_t size, dma_addr_t *dma_handle)
> > +{
> > +       void *buffer = kmalloc(size, GFP_KERNEL);
> > +
> > +       if (!buffer)
> > +               return NULL;
> > +
> > +       *dma_handle = dma_map_single(dev, buffer, size, DMA_FROM_DEVICE);
> > +       if (dma_mapping_error(dev, *dma_handle)) {
> > +               kfree(buffer);
> > +               return NULL;
> > +       }
> > +
> > +       return buffer;
> > +}
> > +
> > +static void pwc_free_urb_buffer(struct device *dev,
> > +                               size_t size,
> > +                               void *buffer,
> > +                               dma_addr_t dma_handle)
> > +{
> > +       dma_unmap_single(dev, dma_handle, size, DMA_FROM_DEVICE);
> > +       kfree(buffer);
> > +}
> > +
> >  static struct pwc_frame_buf *pwc_get_next_fill_buf(struct pwc_device *pdev)
> >  {
> >         unsigned long flags = 0;
> > @@ -306,6 +332,11 @@ static void pwc_isoc_handler(struct urb *urb)
> >         /* Reset ISOC error counter. We did get here, after all. */
> >         pdev->visoc_errors = 0;
> >
> > +       dma_sync_single_for_cpu(&urb->dev->dev,
> > +                               urb->transfer_dma,
> > +                               urb->transfer_buffer_length,
> > +                               DMA_FROM_DEVICE);
> > +
> >         /* vsync: 0 = don't copy data
> >                   1 = sync-hunt
> >                   2 = synched
> > @@ -352,6 +383,11 @@ static void pwc_isoc_handler(struct urb *urb)
> >                 pdev->vlast_packet_size = flen;
> >         }
> >
> > +       dma_sync_single_for_device(&urb->dev->dev,
> > +                                  urb->transfer_dma,
> > +                                  urb->transfer_buffer_length,
> > +                                  DMA_FROM_DEVICE);
> > +
> >  handler_end:
> >         trace_pwc_handler_exit(urb, pdev);
> >
> > @@ -428,16 +464,15 @@ static int pwc_isoc_init(struct pwc_device *pdev)
> >                 urb->dev = udev;
> >                 urb->pipe = usb_rcvisocpipe(udev, pdev->vendpoint);
> >                 urb->transfer_flags = URB_ISO_ASAP | URB_NO_TRANSFER_DMA_MAP;
> > -               urb->transfer_buffer = usb_alloc_coherent(udev,
> > -                                                         ISO_BUFFER_SIZE,
> > -                                                         GFP_KERNEL,
> > -                                                         &urb->transfer_dma);
> > +               urb->transfer_buffer_length = ISO_BUFFER_SIZE;
> > +               urb->transfer_buffer = pwc_alloc_urb_buffer(&udev->dev,
> > +                                                           urb->transfer_buffer_length,
> > +                                                           &urb->transfer_dma);
> >                 if (urb->transfer_buffer == NULL) {
> >                         PWC_ERROR("Failed to allocate urb buffer %d\n", i);
> >                         pwc_isoc_cleanup(pdev);
> >                         return -ENOMEM;
> >                 }
> > -               urb->transfer_buffer_length = ISO_BUFFER_SIZE;
> >                 urb->complete = pwc_isoc_handler;
> >                 urb->context = pdev;
> >                 urb->start_frame = 0;
> > @@ -488,15 +523,16 @@ static void pwc_iso_free(struct pwc_device *pdev)
> >
> >         /* Freeing ISOC buffers one by one */
> >         for (i = 0; i < MAX_ISO_BUFS; i++) {
> > -               if (pdev->urbs[i]) {
> > +               struct urb *urb = pdev->urbs[i];
> > +
> > +               if (urb) {
> >                         PWC_DEBUG_MEMORY("Freeing URB\n");
> > -                       if (pdev->urbs[i]->transfer_buffer) {
> > -                               usb_free_coherent(pdev->udev,
> > -                                       pdev->urbs[i]->transfer_buffer_length,
> > -                                       pdev->urbs[i]->transfer_buffer,
> > -                                       pdev->urbs[i]->transfer_dma);
> > -                       }
> > -                       usb_free_urb(pdev->urbs[i]);
> > +                       if (urb->transfer_buffer)
> > +                               pwc_free_urb_buffer(&urb->dev->dev,
> > +                                                   urb->transfer_buffer_length,
> > +                                                   urb->transfer_buffer,
> > +                                                   urb->transfer_dma);
> > +                       usb_free_urb(urb);
> >                         pdev->urbs[i] = NULL;
> >                 }
> >         }
> > --
> > 2.16.4
> >
>
>
> --
> With best regards,
> Matwey V. Kornilov
Matwey V. Kornilov - Dec. 12, 2018, 1:07 p.m.
??, 30 ????. 2018 ?. ? 15:20, Matwey V. Kornilov <matwey.kornilov@gmail.com>:
>
> ??, 21 ????. 2018 ?. ? 21:15, Matwey V. Kornilov <matwey.kornilov@gmail.com>:
> >
> > ??, 9 ????. 2018 ?. ? 22:03, Matwey V. Kornilov <matwey@sai.msu.ru>:
> > >
> > > DMA cocherency slows the transfer down on systems without hardware
> > > coherent DMA.
> > > Instead we use noncocherent DMA memory and explicit sync at data receive
> > > handler.
> > >
> > > Based on previous commit the following performance benchmarks have been
> > > carried out. Average memcpy() data transfer rate (rate) and handler
> > > completion time (time) have been measured when running video stream at
> > > 640x480 resolution at 10fps.
> > >
> > > x86_64 based system (Intel Core i5-3470). This platform has hardware
> > > coherent DMA support and proposed change doesn't make big difference here.
> > >
> > >  * kmalloc:            rate = (2.0 +- 0.4) GBps
> > >                        time = (5.0 +- 3.0) usec
> > >  * usb_alloc_coherent: rate = (3.4 +- 1.2) GBps
> > >                        time = (3.5 +- 3.0) usec
> > >
> > > We see that the measurements agree within error ranges in this case.
> > > So theoretically predicted performance downgrade cannot be reliably
> > > measured here.
> > >
> > > armv7l based system (TI AM335x BeagleBone Black @ 300MHz). This platform
> > > has no hardware coherent DMA support. DMA coherence is implemented via
> > > disabled page caching that slows down memcpy() due to memory controller
> > > behaviour.
> > >
> > >  * kmalloc:            rate =  ( 94 +- 4) MBps
> > >                        time =  (101 +- 4) usec
> > >  * usb_alloc_coherent: rate = (28.1 +- 0.1) MBps
> > >                        time =  (341 +- 2) usec
> > >
> > > Note, that quantative difference leads (this commit leads to 3.3 times
> > > acceleration) to qualitative behavior change in this case. As it was
> > > stated before, the video stream cannot be successfully received at AM335x
> > > platforms with MUSB based USB host controller due to performance issues
> > > [1].
> > >
> > > [1] https://www.spinics.net/lists/linux-usb/msg165735.html
> > >
> > > Signed-off-by: Matwey V. Kornilov <matwey@sai.msu.ru>
> >
> > Ping
>
> Ping

Ping

>
> >
> > > ---
> > >  drivers/media/usb/pwc/pwc-if.c | 62 +++++++++++++++++++++++++++++++++---------
> > >  1 file changed, 49 insertions(+), 13 deletions(-)
> > >
> > > diff --git a/drivers/media/usb/pwc/pwc-if.c b/drivers/media/usb/pwc/pwc-if.c
> > > index 53c111bd5a22..a81fb319b339 100644
> > > --- a/drivers/media/usb/pwc/pwc-if.c
> > > +++ b/drivers/media/usb/pwc/pwc-if.c
> > > @@ -159,6 +159,32 @@ static const struct video_device pwc_template = {
> > >  /***************************************************************************/
> > >  /* Private functions */
> > >
> > > +static void *pwc_alloc_urb_buffer(struct device *dev,
> > > +                                 size_t size, dma_addr_t *dma_handle)
> > > +{
> > > +       void *buffer = kmalloc(size, GFP_KERNEL);
> > > +
> > > +       if (!buffer)
> > > +               return NULL;
> > > +
> > > +       *dma_handle = dma_map_single(dev, buffer, size, DMA_FROM_DEVICE);
> > > +       if (dma_mapping_error(dev, *dma_handle)) {
> > > +               kfree(buffer);
> > > +               return NULL;
> > > +       }
> > > +
> > > +       return buffer;
> > > +}
> > > +
> > > +static void pwc_free_urb_buffer(struct device *dev,
> > > +                               size_t size,
> > > +                               void *buffer,
> > > +                               dma_addr_t dma_handle)
> > > +{
> > > +       dma_unmap_single(dev, dma_handle, size, DMA_FROM_DEVICE);
> > > +       kfree(buffer);
> > > +}
> > > +
> > >  static struct pwc_frame_buf *pwc_get_next_fill_buf(struct pwc_device *pdev)
> > >  {
> > >         unsigned long flags = 0;
> > > @@ -306,6 +332,11 @@ static void pwc_isoc_handler(struct urb *urb)
> > >         /* Reset ISOC error counter. We did get here, after all. */
> > >         pdev->visoc_errors = 0;
> > >
> > > +       dma_sync_single_for_cpu(&urb->dev->dev,
> > > +                               urb->transfer_dma,
> > > +                               urb->transfer_buffer_length,
> > > +                               DMA_FROM_DEVICE);
> > > +
> > >         /* vsync: 0 = don't copy data
> > >                   1 = sync-hunt
> > >                   2 = synched
> > > @@ -352,6 +383,11 @@ static void pwc_isoc_handler(struct urb *urb)
> > >                 pdev->vlast_packet_size = flen;
> > >         }
> > >
> > > +       dma_sync_single_for_device(&urb->dev->dev,
> > > +                                  urb->transfer_dma,
> > > +                                  urb->transfer_buffer_length,
> > > +                                  DMA_FROM_DEVICE);
> > > +
> > >  handler_end:
> > >         trace_pwc_handler_exit(urb, pdev);
> > >
> > > @@ -428,16 +464,15 @@ static int pwc_isoc_init(struct pwc_device *pdev)
> > >                 urb->dev = udev;
> > >                 urb->pipe = usb_rcvisocpipe(udev, pdev->vendpoint);
> > >                 urb->transfer_flags = URB_ISO_ASAP | URB_NO_TRANSFER_DMA_MAP;
> > > -               urb->transfer_buffer = usb_alloc_coherent(udev,
> > > -                                                         ISO_BUFFER_SIZE,
> > > -                                                         GFP_KERNEL,
> > > -                                                         &urb->transfer_dma);
> > > +               urb->transfer_buffer_length = ISO_BUFFER_SIZE;
> > > +               urb->transfer_buffer = pwc_alloc_urb_buffer(&udev->dev,
> > > +                                                           urb->transfer_buffer_length,
> > > +                                                           &urb->transfer_dma);
> > >                 if (urb->transfer_buffer == NULL) {
> > >                         PWC_ERROR("Failed to allocate urb buffer %d\n", i);
> > >                         pwc_isoc_cleanup(pdev);
> > >                         return -ENOMEM;
> > >                 }
> > > -               urb->transfer_buffer_length = ISO_BUFFER_SIZE;
> > >                 urb->complete = pwc_isoc_handler;
> > >                 urb->context = pdev;
> > >                 urb->start_frame = 0;
> > > @@ -488,15 +523,16 @@ static void pwc_iso_free(struct pwc_device *pdev)
> > >
> > >         /* Freeing ISOC buffers one by one */
> > >         for (i = 0; i < MAX_ISO_BUFS; i++) {
> > > -               if (pdev->urbs[i]) {
> > > +               struct urb *urb = pdev->urbs[i];
> > > +
> > > +               if (urb) {
> > >                         PWC_DEBUG_MEMORY("Freeing URB\n");
> > > -                       if (pdev->urbs[i]->transfer_buffer) {
> > > -                               usb_free_coherent(pdev->udev,
> > > -                                       pdev->urbs[i]->transfer_buffer_length,
> > > -                                       pdev->urbs[i]->transfer_buffer,
> > > -                                       pdev->urbs[i]->transfer_dma);
> > > -                       }
> > > -                       usb_free_urb(pdev->urbs[i]);
> > > +                       if (urb->transfer_buffer)
> > > +                               pwc_free_urb_buffer(&urb->dev->dev,
> > > +                                                   urb->transfer_buffer_length,
> > > +                                                   urb->transfer_buffer,
> > > +                                                   urb->transfer_dma);
> > > +                       usb_free_urb(urb);
> > >                         pdev->urbs[i] = NULL;
> > >                 }
> > >         }
> > > --
> > > 2.16.4
> > >
> >
> >
> > --
> > With best regards,
> > Matwey V. Kornilov
>
>
>
> --
> With best regards,
> Matwey V. Kornilov
Steven Rostedt - Dec. 12, 2018, 1:56 p.m.
Can someone please take this patch or at least say what's wrong with it
if you have a problem?

Matwey has been patiently pinging us once every other week for over a
month asking for a reply. I've already given my Reviewed-by from a
tracing perspective.

Ignoring patches is not a friendly gesture.

-- Steve


On Wed, 12 Dec 2018 16:07:38 +0300
"Matwey V. Kornilov" <matwey.kornilov@gmail.com> wrote:

> ??, 30 ????. 2018 ?. ? 15:20, Matwey V. Kornilov <matwey.kornilov@gmail.com>:
> >
> > ??, 21 ????. 2018 ?. ? 21:15, Matwey V. Kornilov <matwey.kornilov@gmail.com>:  
> > >
> > > ??, 9 ????. 2018 ?. ? 22:03, Matwey V. Kornilov <matwey@sai.msu.ru>:  
> > > >
> > > > DMA cocherency slows the transfer down on systems without hardware
> > > > coherent DMA.
> > > > Instead we use noncocherent DMA memory and explicit sync at data receive
> > > > handler.
> > > >
> > > > Based on previous commit the following performance benchmarks have been
> > > > carried out. Average memcpy() data transfer rate (rate) and handler
> > > > completion time (time) have been measured when running video stream at
> > > > 640x480 resolution at 10fps.
> > > >
> > > > x86_64 based system (Intel Core i5-3470). This platform has hardware
> > > > coherent DMA support and proposed change doesn't make big difference here.
> > > >
> > > >  * kmalloc:            rate = (2.0 +- 0.4) GBps
> > > >                        time = (5.0 +- 3.0) usec
> > > >  * usb_alloc_coherent: rate = (3.4 +- 1.2) GBps
> > > >                        time = (3.5 +- 3.0) usec
> > > >
> > > > We see that the measurements agree within error ranges in this case.
> > > > So theoretically predicted performance downgrade cannot be reliably
> > > > measured here.
> > > >
> > > > armv7l based system (TI AM335x BeagleBone Black @ 300MHz). This platform
> > > > has no hardware coherent DMA support. DMA coherence is implemented via
> > > > disabled page caching that slows down memcpy() due to memory controller
> > > > behaviour.
> > > >
> > > >  * kmalloc:            rate =  ( 94 +- 4) MBps
> > > >                        time =  (101 +- 4) usec
> > > >  * usb_alloc_coherent: rate = (28.1 +- 0.1) MBps
> > > >                        time =  (341 +- 2) usec
> > > >
> > > > Note, that quantative difference leads (this commit leads to 3.3 times
> > > > acceleration) to qualitative behavior change in this case. As it was
> > > > stated before, the video stream cannot be successfully received at AM335x
> > > > platforms with MUSB based USB host controller due to performance issues
> > > > [1].
> > > >
> > > > [1] https://www.spinics.net/lists/linux-usb/msg165735.html
> > > >
> > > > Signed-off-by: Matwey V. Kornilov <matwey@sai.msu.ru>  
> > >
> > > Ping  
> >
> > Ping  
> 
> Ping
> 
> >  
> > >  
> > > > ---
> > > >  drivers/media/usb/pwc/pwc-if.c | 62 +++++++++++++++++++++++++++++++++---------
> > > >  1 file changed, 49 insertions(+), 13 deletions(-)
> > > >
> > > > diff --git a/drivers/media/usb/pwc/pwc-if.c b/drivers/media/usb/pwc/pwc-if.c
> > > > index 53c111bd5a22..a81fb319b339 100644
> > > > --- a/drivers/media/usb/pwc/pwc-if.c
> > > > +++ b/drivers/media/usb/pwc/pwc-if.c
> > > > @@ -159,6 +159,32 @@ static const struct video_device pwc_template = {
> > > >  /***************************************************************************/
> > > >  /* Private functions */
> > > >
> > > > +static void *pwc_alloc_urb_buffer(struct device *dev,
> > > > +                                 size_t size, dma_addr_t *dma_handle)
> > > > +{
> > > > +       void *buffer = kmalloc(size, GFP_KERNEL);
> > > > +
> > > > +       if (!buffer)
> > > > +               return NULL;
> > > > +
> > > > +       *dma_handle = dma_map_single(dev, buffer, size, DMA_FROM_DEVICE);
> > > > +       if (dma_mapping_error(dev, *dma_handle)) {
> > > > +               kfree(buffer);
> > > > +               return NULL;
> > > > +       }
> > > > +
> > > > +       return buffer;
> > > > +}
> > > > +
> > > > +static void pwc_free_urb_buffer(struct device *dev,
> > > > +                               size_t size,
> > > > +                               void *buffer,
> > > > +                               dma_addr_t dma_handle)
> > > > +{
> > > > +       dma_unmap_single(dev, dma_handle, size, DMA_FROM_DEVICE);
> > > > +       kfree(buffer);
> > > > +}
> > > > +
> > > >  static struct pwc_frame_buf *pwc_get_next_fill_buf(struct pwc_device *pdev)
> > > >  {
> > > >         unsigned long flags = 0;
> > > > @@ -306,6 +332,11 @@ static void pwc_isoc_handler(struct urb *urb)
> > > >         /* Reset ISOC error counter. We did get here, after all. */
> > > >         pdev->visoc_errors = 0;
> > > >
> > > > +       dma_sync_single_for_cpu(&urb->dev->dev,
> > > > +                               urb->transfer_dma,
> > > > +                               urb->transfer_buffer_length,
> > > > +                               DMA_FROM_DEVICE);
> > > > +
> > > >         /* vsync: 0 = don't copy data
> > > >                   1 = sync-hunt
> > > >                   2 = synched
> > > > @@ -352,6 +383,11 @@ static void pwc_isoc_handler(struct urb *urb)
> > > >                 pdev->vlast_packet_size = flen;
> > > >         }
> > > >
> > > > +       dma_sync_single_for_device(&urb->dev->dev,
> > > > +                                  urb->transfer_dma,
> > > > +                                  urb->transfer_buffer_length,
> > > > +                                  DMA_FROM_DEVICE);
> > > > +
> > > >  handler_end:
> > > >         trace_pwc_handler_exit(urb, pdev);
> > > >
> > > > @@ -428,16 +464,15 @@ static int pwc_isoc_init(struct pwc_device *pdev)
> > > >                 urb->dev = udev;
> > > >                 urb->pipe = usb_rcvisocpipe(udev, pdev->vendpoint);
> > > >                 urb->transfer_flags = URB_ISO_ASAP | URB_NO_TRANSFER_DMA_MAP;
> > > > -               urb->transfer_buffer = usb_alloc_coherent(udev,
> > > > -                                                         ISO_BUFFER_SIZE,
> > > > -                                                         GFP_KERNEL,
> > > > -                                                         &urb->transfer_dma);
> > > > +               urb->transfer_buffer_length = ISO_BUFFER_SIZE;
> > > > +               urb->transfer_buffer = pwc_alloc_urb_buffer(&udev->dev,
> > > > +                                                           urb->transfer_buffer_length,
> > > > +                                                           &urb->transfer_dma);
> > > >                 if (urb->transfer_buffer == NULL) {
> > > >                         PWC_ERROR("Failed to allocate urb buffer %d\n", i);
> > > >                         pwc_isoc_cleanup(pdev);
> > > >                         return -ENOMEM;
> > > >                 }
> > > > -               urb->transfer_buffer_length = ISO_BUFFER_SIZE;
> > > >                 urb->complete = pwc_isoc_handler;
> > > >                 urb->context = pdev;
> > > >                 urb->start_frame = 0;
> > > > @@ -488,15 +523,16 @@ static void pwc_iso_free(struct pwc_device *pdev)
> > > >
> > > >         /* Freeing ISOC buffers one by one */
> > > >         for (i = 0; i < MAX_ISO_BUFS; i++) {
> > > > -               if (pdev->urbs[i]) {
> > > > +               struct urb *urb = pdev->urbs[i];
> > > > +
> > > > +               if (urb) {
> > > >                         PWC_DEBUG_MEMORY("Freeing URB\n");
> > > > -                       if (pdev->urbs[i]->transfer_buffer) {
> > > > -                               usb_free_coherent(pdev->udev,
> > > > -                                       pdev->urbs[i]->transfer_buffer_length,
> > > > -                                       pdev->urbs[i]->transfer_buffer,
> > > > -                                       pdev->urbs[i]->transfer_dma);
> > > > -                       }
> > > > -                       usb_free_urb(pdev->urbs[i]);
> > > > +                       if (urb->transfer_buffer)
> > > > +                               pwc_free_urb_buffer(&urb->dev->dev,
> > > > +                                                   urb->transfer_buffer_length,
> > > > +                                                   urb->transfer_buffer,
> > > > +                                                   urb->transfer_dma);
> > > > +                       usb_free_urb(urb);
> > > >                         pdev->urbs[i] = NULL;
> > > >                 }
> > > >         }
> > > > --
> > > > 2.16.4
> > > >  
> > >
> > >
> > > --
> > > With best regards,
> > > Matwey V. Kornilov  
> >
> >
> >
> > --
> > With best regards,
> > Matwey V. Kornilov  
> 
> 
>
Steven Rostedt - Dec. 12, 2018, 2:01 p.m.
On Wed, 12 Dec 2018 08:56:22 -0500
Steven Rostedt <rostedt@goodmis.org> wrote:

> Can someone please take this patch or at least say what's wrong with it
> if you have a problem?
> 
> Matwey has been patiently pinging us once every other week for over a
> month asking for a reply. I've already given my Reviewed-by from a
> tracing perspective.
> 
> Ignoring patches is not a friendly gesture.
> 

Nevermind, it appears that v5 is still under discussion.

Matwey, does v6 address the comments made in v5?

-- Steve
Matwey V. Kornilov - Dec. 12, 2018, 3:15 p.m.
??, 12 ???. 2018 ?. ? 17:01, Steven Rostedt <rostedt@goodmis.org>:
>
> On Wed, 12 Dec 2018 08:56:22 -0500
> Steven Rostedt <rostedt@goodmis.org> wrote:
>
> > Can someone please take this patch or at least say what's wrong with it
> > if you have a problem?
> >
> > Matwey has been patiently pinging us once every other week for over a
> > month asking for a reply. I've already given my Reviewed-by from a
> > tracing perspective.
> >
> > Ignoring patches is not a friendly gesture.
> >
>
> Nevermind, it appears that v5 is still under discussion.
>
> Matwey, does v6 address the comments made in v5?

Hi,

v6 addresses the comments made by Laurent Pinchart on Oct, 31:

https://www.spinics.net/lists/linux-media/msg142216.html

namely, dma_sync_single_for_device() is introduced in the proper place



>
> -- Steve

Patch

diff --git a/drivers/media/usb/pwc/pwc-if.c b/drivers/media/usb/pwc/pwc-if.c
index 53c111bd5a22..a81fb319b339 100644
--- a/drivers/media/usb/pwc/pwc-if.c
+++ b/drivers/media/usb/pwc/pwc-if.c
@@ -159,6 +159,32 @@  static const struct video_device pwc_template = {
 /***************************************************************************/
 /* Private functions */
 
+static void *pwc_alloc_urb_buffer(struct device *dev,
+				  size_t size, dma_addr_t *dma_handle)
+{
+	void *buffer = kmalloc(size, GFP_KERNEL);
+
+	if (!buffer)
+		return NULL;
+
+	*dma_handle = dma_map_single(dev, buffer, size, DMA_FROM_DEVICE);
+	if (dma_mapping_error(dev, *dma_handle)) {
+		kfree(buffer);
+		return NULL;
+	}
+
+	return buffer;
+}
+
+static void pwc_free_urb_buffer(struct device *dev,
+				size_t size,
+				void *buffer,
+				dma_addr_t dma_handle)
+{
+	dma_unmap_single(dev, dma_handle, size, DMA_FROM_DEVICE);
+	kfree(buffer);
+}
+
 static struct pwc_frame_buf *pwc_get_next_fill_buf(struct pwc_device *pdev)
 {
 	unsigned long flags = 0;
@@ -306,6 +332,11 @@  static void pwc_isoc_handler(struct urb *urb)
 	/* Reset ISOC error counter. We did get here, after all. */
 	pdev->visoc_errors = 0;
 
+	dma_sync_single_for_cpu(&urb->dev->dev,
+				urb->transfer_dma,
+				urb->transfer_buffer_length,
+				DMA_FROM_DEVICE);
+
 	/* vsync: 0 = don't copy data
 		  1 = sync-hunt
 		  2 = synched
@@ -352,6 +383,11 @@  static void pwc_isoc_handler(struct urb *urb)
 		pdev->vlast_packet_size = flen;
 	}
 
+	dma_sync_single_for_device(&urb->dev->dev,
+				   urb->transfer_dma,
+				   urb->transfer_buffer_length,
+				   DMA_FROM_DEVICE);
+
 handler_end:
 	trace_pwc_handler_exit(urb, pdev);
 
@@ -428,16 +464,15 @@  static int pwc_isoc_init(struct pwc_device *pdev)
 		urb->dev = udev;
 		urb->pipe = usb_rcvisocpipe(udev, pdev->vendpoint);
 		urb->transfer_flags = URB_ISO_ASAP | URB_NO_TRANSFER_DMA_MAP;
-		urb->transfer_buffer = usb_alloc_coherent(udev,
-							  ISO_BUFFER_SIZE,
-							  GFP_KERNEL,
-							  &urb->transfer_dma);
+		urb->transfer_buffer_length = ISO_BUFFER_SIZE;
+		urb->transfer_buffer = pwc_alloc_urb_buffer(&udev->dev,
+							    urb->transfer_buffer_length,
+							    &urb->transfer_dma);
 		if (urb->transfer_buffer == NULL) {
 			PWC_ERROR("Failed to allocate urb buffer %d\n", i);
 			pwc_isoc_cleanup(pdev);
 			return -ENOMEM;
 		}
-		urb->transfer_buffer_length = ISO_BUFFER_SIZE;
 		urb->complete = pwc_isoc_handler;
 		urb->context = pdev;
 		urb->start_frame = 0;
@@ -488,15 +523,16 @@  static void pwc_iso_free(struct pwc_device *pdev)
 
 	/* Freeing ISOC buffers one by one */
 	for (i = 0; i < MAX_ISO_BUFS; i++) {
-		if (pdev->urbs[i]) {
+		struct urb *urb = pdev->urbs[i];
+
+		if (urb) {
 			PWC_DEBUG_MEMORY("Freeing URB\n");
-			if (pdev->urbs[i]->transfer_buffer) {
-				usb_free_coherent(pdev->udev,
-					pdev->urbs[i]->transfer_buffer_length,
-					pdev->urbs[i]->transfer_buffer,
-					pdev->urbs[i]->transfer_dma);
-			}
-			usb_free_urb(pdev->urbs[i]);
+			if (urb->transfer_buffer)
+				pwc_free_urb_buffer(&urb->dev->dev,
+						    urb->transfer_buffer_length,
+						    urb->transfer_buffer,
+						    urb->transfer_dma);
+			usb_free_urb(urb);
 			pdev->urbs[i] = NULL;
 		}
 	}

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