[FFmpeg-devel,3/6] avutil/hwcontext_cuda: add CUstream in cuda hwctx

Submitted by Timo Rothenpieler on May 8, 2018, 1:31 p.m.

Details

Message ID 20180508133132.28940-3-timo@rothenpieler.org
State New
Headers show

Commit Message

Timo Rothenpieler May 8, 2018, 1:31 p.m.
---
 configure                  | 6 ++++--
 doc/APIchanges             | 3 ++-
 libavutil/hwcontext_cuda.c | 3 +++
 libavutil/hwcontext_cuda.h | 1 +
 libavutil/version.h        | 2 +-
 5 files changed, 11 insertions(+), 4 deletions(-)

Comments

wm4 May 8, 2018, 3:26 p.m.
On Tue,  8 May 2018 15:31:29 +0200
Timo Rothenpieler <timo@rothenpieler.org> wrote:

> ---
>  configure                  | 6 ++++--
>  doc/APIchanges             | 3 ++-
>  libavutil/hwcontext_cuda.c | 3 +++
>  libavutil/hwcontext_cuda.h | 1 +
>  libavutil/version.h        | 2 +-
>  5 files changed, 11 insertions(+), 4 deletions(-)
> 
> diff --git a/configure b/configure
> index 7c143238a8..cae8a235a4 100755
> --- a/configure
> +++ b/configure
> @@ -5887,8 +5887,10 @@ check_type "va/va.h va/va_enc_vp9.h"  "VAEncPictureParameterBufferVP9"
>  check_type "vdpau/vdpau.h" "VdpPictureInfoHEVC"
>  
>  if ! disabled ffnvcodec; then
> -    check_pkg_config ffnvcodec "ffnvcodec >= 8.0.14.1" \
> -        "ffnvcodec/nvEncodeAPI.h ffnvcodec/dynlink_cuda.h ffnvcodec/dynlink_cuviddec.h ffnvcodec/dynlink_nvcuvid.h" ""
> +    check_pkg_config ffnvcodec "ffnvcodec >= 8.1.24.2" \
> +          "ffnvcodec/nvEncodeAPI.h ffnvcodec/dynlink_cuda.h ffnvcodec/dynlink_cuviddec.h ffnvcodec/dynlink_nvcuvid.h" "" || \
> +        { test_pkg_config ffnvcodec_tmp "ffnvcodec < 8.1" "" "" && check_pkg_config ffnvcodec "ffnvcodec >= 8.0.14.2" \
> +          "ffnvcodec/nvEncodeAPI.h ffnvcodec/dynlink_cuda.h ffnvcodec/dynlink_cuviddec.h ffnvcodec/dynlink_nvcuvid.h" ""; }
>  fi
>  
>  check_cpp_condition winrt windows.h "!WINAPI_FAMILY_PARTITION(WINAPI_PARTITION_DESKTOP)"
> diff --git a/doc/APIchanges b/doc/APIchanges
> index f8ae6b0433..7a0a8522f9 100644
> --- a/doc/APIchanges
> +++ b/doc/APIchanges
> @@ -15,8 +15,9 @@ libavutil:     2017-10-21
>  
>  API changes, most recent first:
>  
> -2018-05-xx - xxxxxxxxxx - lavu 56.19.100 - hwcontext_cuda.h
> +2018-05-xx - xxxxxxxxxx, xxxxxxxxxx - lavu 56.19.100/101 - hwcontext_cuda.h
>    Add AVCUDAFramesContext and AVCUDAFramesContext.flags.
> +  Add AVCUDADeviceContext.stream.
>  
>  2018-04-xx - xxxxxxxxxx - lavu 56.18.100 - pixdesc.h
>    Add AV_PIX_FMT_FLAG_ALPHA to AV_PIX_FMT_PAL8.
> diff --git a/libavutil/hwcontext_cuda.c b/libavutil/hwcontext_cuda.c
> index b0b4bf24ae..8024eec79d 100644
> --- a/libavutil/hwcontext_cuda.c
> +++ b/libavutil/hwcontext_cuda.c
> @@ -395,6 +395,9 @@ static int cuda_device_create(AVHWDeviceContext *ctx, const char *device,
>          goto error;
>      }
>  
> +    // Setting stream to NULL will make functions automatically use the default CUstream
> +    hwctx->stream = NULL;
> +
>      cu->cuCtxPopCurrent(&dummy);
>  
>      hwctx->internal->is_allocated = 1;
> diff --git a/libavutil/hwcontext_cuda.h b/libavutil/hwcontext_cuda.h
> index 19accbd9be..cd797ae920 100644
> --- a/libavutil/hwcontext_cuda.h
> +++ b/libavutil/hwcontext_cuda.h
> @@ -41,6 +41,7 @@ typedef struct AVCUDADeviceContextInternal AVCUDADeviceContextInternal;
>   */
>  typedef struct AVCUDADeviceContext {
>      CUcontext cuda_ctx;
> +    CUstream stream;
>      AVCUDADeviceContextInternal *internal;
>  } AVCUDADeviceContext;
>  
> diff --git a/libavutil/version.h b/libavutil/version.h
> index 84409b1d69..f84ec89154 100644
> --- a/libavutil/version.h
> +++ b/libavutil/version.h
> @@ -80,7 +80,7 @@
>  
>  #define LIBAVUTIL_VERSION_MAJOR  56
>  #define LIBAVUTIL_VERSION_MINOR  19
> -#define LIBAVUTIL_VERSION_MICRO 100
> +#define LIBAVUTIL_VERSION_MICRO 101
>  
>  #define LIBAVUTIL_VERSION_INT   AV_VERSION_INT(LIBAVUTIL_VERSION_MAJOR, \
>                                                 LIBAVUTIL_VERSION_MINOR, \

What is this?
Timo Rothenpieler May 8, 2018, 3:48 p.m.
Am 08.05.2018 um 17:26 schrieb wm4:
> On Tue,  8 May 2018 15:31:29 +0200
> Timo Rothenpieler <timo@rothenpieler.org> wrote:
> 
>> ---
>>   configure                  | 6 ++++--
>>   doc/APIchanges             | 3 ++-
>>   libavutil/hwcontext_cuda.c | 3 +++
>>   libavutil/hwcontext_cuda.h | 1 +
>>   libavutil/version.h        | 2 +-
>>   5 files changed, 11 insertions(+), 4 deletions(-)
>>
>> diff --git a/configure b/configure
>> index 7c143238a8..cae8a235a4 100755
>> --- a/configure
>> +++ b/configure
>> @@ -5887,8 +5887,10 @@ check_type "va/va.h va/va_enc_vp9.h"  "VAEncPictureParameterBufferVP9"
>>   check_type "vdpau/vdpau.h" "VdpPictureInfoHEVC"
>>   
>>   if ! disabled ffnvcodec; then
>> -    check_pkg_config ffnvcodec "ffnvcodec >= 8.0.14.1" \
>> -        "ffnvcodec/nvEncodeAPI.h ffnvcodec/dynlink_cuda.h ffnvcodec/dynlink_cuviddec.h ffnvcodec/dynlink_nvcuvid.h" ""
>> +    check_pkg_config ffnvcodec "ffnvcodec >= 8.1.24.2" \
>> +          "ffnvcodec/nvEncodeAPI.h ffnvcodec/dynlink_cuda.h ffnvcodec/dynlink_cuviddec.h ffnvcodec/dynlink_nvcuvid.h" "" || \
>> +        { test_pkg_config ffnvcodec_tmp "ffnvcodec < 8.1" "" "" && check_pkg_config ffnvcodec "ffnvcodec >= 8.0.14.2" \
>> +          "ffnvcodec/nvEncodeAPI.h ffnvcodec/dynlink_cuda.h ffnvcodec/dynlink_cuviddec.h ffnvcodec/dynlink_nvcuvid.h" ""; }
>>   fi
>>   
>>   check_cpp_condition winrt windows.h "!WINAPI_FAMILY_PARTITION(WINAPI_PARTITION_DESKTOP)"
>> diff --git a/doc/APIchanges b/doc/APIchanges
>> index f8ae6b0433..7a0a8522f9 100644
>> --- a/doc/APIchanges
>> +++ b/doc/APIchanges
>> @@ -15,8 +15,9 @@ libavutil:     2017-10-21
>>   
>>   API changes, most recent first:
>>   
>> -2018-05-xx - xxxxxxxxxx - lavu 56.19.100 - hwcontext_cuda.h
>> +2018-05-xx - xxxxxxxxxx, xxxxxxxxxx - lavu 56.19.100/101 - hwcontext_cuda.h
>>     Add AVCUDAFramesContext and AVCUDAFramesContext.flags.
>> +  Add AVCUDADeviceContext.stream.
>>   
>>   2018-04-xx - xxxxxxxxxx - lavu 56.18.100 - pixdesc.h
>>     Add AV_PIX_FMT_FLAG_ALPHA to AV_PIX_FMT_PAL8.
>> diff --git a/libavutil/hwcontext_cuda.c b/libavutil/hwcontext_cuda.c
>> index b0b4bf24ae..8024eec79d 100644
>> --- a/libavutil/hwcontext_cuda.c
>> +++ b/libavutil/hwcontext_cuda.c
>> @@ -395,6 +395,9 @@ static int cuda_device_create(AVHWDeviceContext *ctx, const char *device,
>>           goto error;
>>       }
>>   
>> +    // Setting stream to NULL will make functions automatically use the default CUstream
>> +    hwctx->stream = NULL;
>> +
>>       cu->cuCtxPopCurrent(&dummy);
>>   
>>       hwctx->internal->is_allocated = 1;
>> diff --git a/libavutil/hwcontext_cuda.h b/libavutil/hwcontext_cuda.h
>> index 19accbd9be..cd797ae920 100644
>> --- a/libavutil/hwcontext_cuda.h
>> +++ b/libavutil/hwcontext_cuda.h
>> @@ -41,6 +41,7 @@ typedef struct AVCUDADeviceContextInternal AVCUDADeviceContextInternal;
>>    */
>>   typedef struct AVCUDADeviceContext {
>>       CUcontext cuda_ctx;
>> +    CUstream stream;
>>       AVCUDADeviceContextInternal *internal;
>>   } AVCUDADeviceContext;
>>   
>> diff --git a/libavutil/version.h b/libavutil/version.h
>> index 84409b1d69..f84ec89154 100644
>> --- a/libavutil/version.h
>> +++ b/libavutil/version.h
>> @@ -80,7 +80,7 @@
>>   
>>   #define LIBAVUTIL_VERSION_MAJOR  56
>>   #define LIBAVUTIL_VERSION_MINOR  19
>> -#define LIBAVUTIL_VERSION_MICRO 100
>> +#define LIBAVUTIL_VERSION_MICRO 101
>>   
>>   #define LIBAVUTIL_VERSION_INT   AV_VERSION_INT(LIBAVUTIL_VERSION_MAJOR, \
>>                                                  LIBAVUTIL_VERSION_MINOR, \
> 
> What is this?

https://docs.nvidia.com/cuda/cuda-driver-api/stream-sync-behavior.html

It allows asynchronous processing of CUDA workloads. The next couple 
patches make use of it.
There's no change in behaviour if it remains unset/NULL, but if you set 
one, the workload won't block the main CUDA stream so you can do 
multiple transcode sessions in the same application without blocking one 
another.
wm4 May 8, 2018, 3:55 p.m.
On Tue, 8 May 2018 17:48:21 +0200
Timo Rothenpieler <timo@rothenpieler.org> wrote:

> Am 08.05.2018 um 17:26 schrieb wm4:
> > On Tue,  8 May 2018 15:31:29 +0200
> > Timo Rothenpieler <timo@rothenpieler.org> wrote:
> >   
> >> ---
> >>   configure                  | 6 ++++--
> >>   doc/APIchanges             | 3 ++-
> >>   libavutil/hwcontext_cuda.c | 3 +++
> >>   libavutil/hwcontext_cuda.h | 1 +
> >>   libavutil/version.h        | 2 +-
> >>   5 files changed, 11 insertions(+), 4 deletions(-)
> >>
> >> diff --git a/configure b/configure
> >> index 7c143238a8..cae8a235a4 100755
> >> --- a/configure
> >> +++ b/configure
> >> @@ -5887,8 +5887,10 @@ check_type "va/va.h va/va_enc_vp9.h"  "VAEncPictureParameterBufferVP9"
> >>   check_type "vdpau/vdpau.h" "VdpPictureInfoHEVC"
> >>   
> >>   if ! disabled ffnvcodec; then
> >> -    check_pkg_config ffnvcodec "ffnvcodec >= 8.0.14.1" \
> >> -        "ffnvcodec/nvEncodeAPI.h ffnvcodec/dynlink_cuda.h ffnvcodec/dynlink_cuviddec.h ffnvcodec/dynlink_nvcuvid.h" ""
> >> +    check_pkg_config ffnvcodec "ffnvcodec >= 8.1.24.2" \
> >> +          "ffnvcodec/nvEncodeAPI.h ffnvcodec/dynlink_cuda.h ffnvcodec/dynlink_cuviddec.h ffnvcodec/dynlink_nvcuvid.h" "" || \
> >> +        { test_pkg_config ffnvcodec_tmp "ffnvcodec < 8.1" "" "" && check_pkg_config ffnvcodec "ffnvcodec >= 8.0.14.2" \
> >> +          "ffnvcodec/nvEncodeAPI.h ffnvcodec/dynlink_cuda.h ffnvcodec/dynlink_cuviddec.h ffnvcodec/dynlink_nvcuvid.h" ""; }
> >>   fi
> >>   
> >>   check_cpp_condition winrt windows.h "!WINAPI_FAMILY_PARTITION(WINAPI_PARTITION_DESKTOP)"
> >> diff --git a/doc/APIchanges b/doc/APIchanges
> >> index f8ae6b0433..7a0a8522f9 100644
> >> --- a/doc/APIchanges
> >> +++ b/doc/APIchanges
> >> @@ -15,8 +15,9 @@ libavutil:     2017-10-21
> >>   
> >>   API changes, most recent first:
> >>   
> >> -2018-05-xx - xxxxxxxxxx - lavu 56.19.100 - hwcontext_cuda.h
> >> +2018-05-xx - xxxxxxxxxx, xxxxxxxxxx - lavu 56.19.100/101 - hwcontext_cuda.h
> >>     Add AVCUDAFramesContext and AVCUDAFramesContext.flags.
> >> +  Add AVCUDADeviceContext.stream.
> >>   
> >>   2018-04-xx - xxxxxxxxxx - lavu 56.18.100 - pixdesc.h
> >>     Add AV_PIX_FMT_FLAG_ALPHA to AV_PIX_FMT_PAL8.
> >> diff --git a/libavutil/hwcontext_cuda.c b/libavutil/hwcontext_cuda.c
> >> index b0b4bf24ae..8024eec79d 100644
> >> --- a/libavutil/hwcontext_cuda.c
> >> +++ b/libavutil/hwcontext_cuda.c
> >> @@ -395,6 +395,9 @@ static int cuda_device_create(AVHWDeviceContext *ctx, const char *device,
> >>           goto error;
> >>       }
> >>   
> >> +    // Setting stream to NULL will make functions automatically use the default CUstream
> >> +    hwctx->stream = NULL;
> >> +
> >>       cu->cuCtxPopCurrent(&dummy);
> >>   
> >>       hwctx->internal->is_allocated = 1;
> >> diff --git a/libavutil/hwcontext_cuda.h b/libavutil/hwcontext_cuda.h
> >> index 19accbd9be..cd797ae920 100644
> >> --- a/libavutil/hwcontext_cuda.h
> >> +++ b/libavutil/hwcontext_cuda.h
> >> @@ -41,6 +41,7 @@ typedef struct AVCUDADeviceContextInternal AVCUDADeviceContextInternal;
> >>    */
> >>   typedef struct AVCUDADeviceContext {
> >>       CUcontext cuda_ctx;
> >> +    CUstream stream;
> >>       AVCUDADeviceContextInternal *internal;
> >>   } AVCUDADeviceContext;
> >>   
> >> diff --git a/libavutil/version.h b/libavutil/version.h
> >> index 84409b1d69..f84ec89154 100644
> >> --- a/libavutil/version.h
> >> +++ b/libavutil/version.h
> >> @@ -80,7 +80,7 @@
> >>   
> >>   #define LIBAVUTIL_VERSION_MAJOR  56
> >>   #define LIBAVUTIL_VERSION_MINOR  19
> >> -#define LIBAVUTIL_VERSION_MICRO 100
> >> +#define LIBAVUTIL_VERSION_MICRO 101
> >>   
> >>   #define LIBAVUTIL_VERSION_INT   AV_VERSION_INT(LIBAVUTIL_VERSION_MAJOR, \
> >>                                                  LIBAVUTIL_VERSION_MINOR, \  
> > 
> > What is this?  
> 
> https://docs.nvidia.com/cuda/cuda-driver-api/stream-sync-behavior.html
> 
> It allows asynchronous processing of CUDA workloads. The next couple 
> patches make use of it.
> There's no change in behaviour if it remains unset/NULL, but if you set 
> one, the workload won't block the main CUDA stream so you can do 
> multiple transcode sessions in the same application without blocking one 
> another.
> 

Could probably be documented.

It seems a bit strange that this is per device. Wouldn't it be per
operation?
Timo Rothenpieler May 8, 2018, 4:32 p.m.
>>> What is this?
>>
>> https://docs.nvidia.com/cuda/cuda-driver-api/stream-sync-behavior.html
>>
>> It allows asynchronous processing of CUDA workloads. The next couple
>> patches make use of it.
>> There's no change in behaviour if it remains unset/NULL, but if you set
>> one, the workload won't block the main CUDA stream so you can do
>> multiple transcode sessions in the same application without blocking one
>> another.
>>
> 
> Could probably be documented.
> 
> It seems a bit strange that this is per device. Wouldn't it be per
> operation?

The whole streams thing and its various modes of operation are a bit 
strange. But it does make things faster in certain conditions.

See the whole thread with Oscar Amoros Huguet <oamoros@mediapro.tv> 
about some background on it.
Oscar Amoros Huguet May 8, 2018, 9:11 p.m.
Hi!

Responding the per device question (sorry I can't make it shorter, the topic is quite dense).

A typical CUDA application uses a single cuda context, and multiple cuda streams to allow asynchronicity between cuda tasks (memory transfers, kernels, memsets) and make overlapping between those tasks possible, to save potentially a lot to execution time.

Even with Timo's changes, by default the behaviour of ffmpeg is the same. Each ffmpeg decoding instance creates a new cuda context by calling cuda_device_create.

The result of this, can be seen with (for instance) NVIDIA NSIGHT Visual Studio plugin timeline. Basically, the GPU changes it's cuda context every frame, as many times as videos you are decoding. This is less optimal than what is possible with Timo's additions.

The reason for the un-efficiency is partly because of the time the GPU needs to change between contexts (very small in recent hardware), but also and more importantly, because any cuda task executing in a cuda context, will never overlap with tasks in other cuda contexts. And this can imply a huge waste of time, specially if you need to download each frame from GPU to CPU.

Before Timo's changes, I could already use the same cuda contex for all decoding instances, using a CPU thread per video, that will not call cuda_device_create. Instead, each thread will allocate an ffmpeg hw_ctx, and manually set the cuda contex that already exists in the application. This way you solve the problem of switching contexts, and another problem. All cuda tasks enqueued by nvdec and ffmpeg for the decoding task, now are using the default stream of the same cuda context, so now I can synchronize this default stream, with another non-default stream in my aplication, making all the following cuda tasks to be asynchronous and able to overlap. Before, I had to copy the data from GPU to CPU in a blocking way, indirectly using the context created by ffmpeg. But still, the cuda tasks enqueued by nvdec and ffmpeg are not overlapping because they are not asynchronous, because they use the default cuda stream.

So now, we are using the same "device" or cuda context for all decoding feeds in the application.

Thanks to Timo's changes, besides the removal of some memory copies (very nice), now additionally to being able to manually set the cuda context, I can set a non-default cuda stream in the ffmpeg cuda hw_ctx struct, so all cuda tasks performed by ffmpeg and nvdec will use this stream, and can overlap with all my other cuda tasks, instead of blocking the gpu until they finish.

I our use case, this is a very relevant execution time improvement, and we are going to use this. So I hope this, or something similar can go into the master branch of the project.

Hope my explanation is useful.

Oscar

Patch hide | download patch | download mbox

diff --git a/configure b/configure
index 7c143238a8..cae8a235a4 100755
--- a/configure
+++ b/configure
@@ -5887,8 +5887,10 @@  check_type "va/va.h va/va_enc_vp9.h"  "VAEncPictureParameterBufferVP9"
 check_type "vdpau/vdpau.h" "VdpPictureInfoHEVC"
 
 if ! disabled ffnvcodec; then
-    check_pkg_config ffnvcodec "ffnvcodec >= 8.0.14.1" \
-        "ffnvcodec/nvEncodeAPI.h ffnvcodec/dynlink_cuda.h ffnvcodec/dynlink_cuviddec.h ffnvcodec/dynlink_nvcuvid.h" ""
+    check_pkg_config ffnvcodec "ffnvcodec >= 8.1.24.2" \
+          "ffnvcodec/nvEncodeAPI.h ffnvcodec/dynlink_cuda.h ffnvcodec/dynlink_cuviddec.h ffnvcodec/dynlink_nvcuvid.h" "" || \
+        { test_pkg_config ffnvcodec_tmp "ffnvcodec < 8.1" "" "" && check_pkg_config ffnvcodec "ffnvcodec >= 8.0.14.2" \
+          "ffnvcodec/nvEncodeAPI.h ffnvcodec/dynlink_cuda.h ffnvcodec/dynlink_cuviddec.h ffnvcodec/dynlink_nvcuvid.h" ""; }
 fi
 
 check_cpp_condition winrt windows.h "!WINAPI_FAMILY_PARTITION(WINAPI_PARTITION_DESKTOP)"
diff --git a/doc/APIchanges b/doc/APIchanges
index f8ae6b0433..7a0a8522f9 100644
--- a/doc/APIchanges
+++ b/doc/APIchanges
@@ -15,8 +15,9 @@  libavutil:     2017-10-21
 
 API changes, most recent first:
 
-2018-05-xx - xxxxxxxxxx - lavu 56.19.100 - hwcontext_cuda.h
+2018-05-xx - xxxxxxxxxx, xxxxxxxxxx - lavu 56.19.100/101 - hwcontext_cuda.h
   Add AVCUDAFramesContext and AVCUDAFramesContext.flags.
+  Add AVCUDADeviceContext.stream.
 
 2018-04-xx - xxxxxxxxxx - lavu 56.18.100 - pixdesc.h
   Add AV_PIX_FMT_FLAG_ALPHA to AV_PIX_FMT_PAL8.
diff --git a/libavutil/hwcontext_cuda.c b/libavutil/hwcontext_cuda.c
index b0b4bf24ae..8024eec79d 100644
--- a/libavutil/hwcontext_cuda.c
+++ b/libavutil/hwcontext_cuda.c
@@ -395,6 +395,9 @@  static int cuda_device_create(AVHWDeviceContext *ctx, const char *device,
         goto error;
     }
 
+    // Setting stream to NULL will make functions automatically use the default CUstream
+    hwctx->stream = NULL;
+
     cu->cuCtxPopCurrent(&dummy);
 
     hwctx->internal->is_allocated = 1;
diff --git a/libavutil/hwcontext_cuda.h b/libavutil/hwcontext_cuda.h
index 19accbd9be..cd797ae920 100644
--- a/libavutil/hwcontext_cuda.h
+++ b/libavutil/hwcontext_cuda.h
@@ -41,6 +41,7 @@  typedef struct AVCUDADeviceContextInternal AVCUDADeviceContextInternal;
  */
 typedef struct AVCUDADeviceContext {
     CUcontext cuda_ctx;
+    CUstream stream;
     AVCUDADeviceContextInternal *internal;
 } AVCUDADeviceContext;
 
diff --git a/libavutil/version.h b/libavutil/version.h
index 84409b1d69..f84ec89154 100644
--- a/libavutil/version.h
+++ b/libavutil/version.h
@@ -80,7 +80,7 @@ 
 
 #define LIBAVUTIL_VERSION_MAJOR  56
 #define LIBAVUTIL_VERSION_MINOR  19
-#define LIBAVUTIL_VERSION_MICRO 100
+#define LIBAVUTIL_VERSION_MICRO 101
 
 #define LIBAVUTIL_VERSION_INT   AV_VERSION_INT(LIBAVUTIL_VERSION_MAJOR, \
                                                LIBAVUTIL_VERSION_MINOR, \