[FFmpeg-devel] [PATCH] Allow using primary CUDA device context
Timo Rothenpieler
timo at rothenpieler.org
Mon Nov 18 13:09:26 EET 2019
On 18/11/2019 11:51, Oleg Dobkin wrote:
> I've changed enum into a flag and moved it into
> AVCUDADeviceContextInternal.
>
>> Can't one just call cuCtxGetDevice on the context to get the device?
>
> Not sure the cuCtxGetDevice can be used for the primary context; also,
> according to documentation it returns device id not handle. Anyway, is
> it that bad to store an additional handle?
It's public API, and once something is there, it has to stay there for
quite a while. So I'm not too much a fan of adding something there,
which can already easily be gotten from existing fields.
The CUdevice, which you intended to store there, and which
cuCtxGetDevice returns, _is_ the device ID. It's a typedef to int.
I'm not aware of there being anything beyond that.
Storing it in the internal struct is fine though, for the sake of not
having to call cuCtxGetDevice each time.
>> Also needs configure updated for the higher ffnvcodec version
>
> I'm looking at the configure and can't figure out how ffnvcodec version
> is enforced. The script seems to accept several ranges of ffnvcodec
> versions. I could just increment the top-level check, but I'm not sure
> this is the correct way.
FFmpeg supports multiple tracks of the Video Codec SDK, to support older
drivers and legacy GPUs that way.
Since the version number only tracks the Video SDK Version, and not the
CUDA loader version, what needs to be done is to set the new minimum
version for each supported track.
So far, there was no need to add explicit checks for SDK 9.1, but that
will be required for this.
Also, since SDK 8.0 is effectively dead, it can be dropped.
I immediately bump the version on ffnvcodec git after every release, so
the correct versions to check for in configure right now are:
9.1.23.1, 9.0.18.3, 8.2.15.10 and 8.1.24.11
> On Sun, 2019-11-17 at 23:31 +0100, Timo Rothenpieler wrote:
>> On 17.11.2019 15:58, Oleg Dobkin wrote:
>>
>> Add AVCUDADeviceContextFlags to control the creation of CUDA device
>> context for the hardware CUDA decoder.
>>
>> The current values are 0 (default behavior) - new context will be
>> created for each decoder, and 1 - primary CUDA context will be used.
>>
>> There are several reasons for using primary device context instead of
>> creating a new one:
>>
>> - This is the recommended way to handle device contexts (see
>>
> https://docs.nvidia.com/cuda/cuda-driver-api/group__CUDA__CTX.html#group__CUDA__CTX_1g65dc0012348bc84810e2103a40d8e2cf
>> )
>>
>> - Memory allocations, kernels and other state are associated with
>> the
>> current device context. Currently, the context is not accessible from
>> FFmpeg API, so, technically, the memory created by the hardware
>> decoder
>> (the video frame) can't be safely read.
>>
>> Signed-off-by: Oleg Dobkin <olegd at anyvision.co>
>> ---
>> libavutil/hwcontext_cuda.c | 20 +++++++++++++++-----
>> libavutil/hwcontext_cuda.h | 7 +++++++
>> 2 files changed, 22 insertions(+), 5 deletions(-)
>>
>> diff --git a/libavutil/hwcontext_cuda.c b/libavutil/hwcontext_cuda.c
>> index cca39e9fc7..608ea57569 100644
>> --- a/libavutil/hwcontext_cuda.c
>> +++ b/libavutil/hwcontext_cuda.c
>> @@ -281,8 +281,12 @@ static void cuda_device_uninit(AVHWDeviceContext
>> *device_ctx)
>> if (hwctx->internal) {
>> CudaFunctions *cu = hwctx->internal->cuda_dl;
>> if (hwctx->internal->is_allocated && hwctx->cuda_ctx) {
>> - CHECK_CU(cu->cuCtxDestroy(hwctx->cuda_ctx));
>> + if (hwctx->flags == DCF_CREATE_CONTEXT)
>>
>> Should actually be checking for the flag, not equality.
>>
>>
>> + CHECK_CU(cu->cuCtxDestroy(hwctx->cuda_ctx));
>> + else
>> + CHECK_CU(cu->cuDevicePrimaryCtxRelease(hwctx-
>>> cuda_device));
>> hwctx->cuda_ctx = NULL;
>> + hwctx->cuda_device = NULL;
>> }
>> cuda_free_functions(&hwctx->internal->cuda_dl);
>> }
>> @@ -322,7 +326,6 @@ static int cuda_device_create(AVHWDeviceContext
>> *device_ctx,
>> {
>> AVCUDADeviceContext *hwctx = device_ctx->hwctx;
>> CudaFunctions *cu;
>> - CUdevice cu_device;
>> CUcontext dummy;
>> int ret, device_idx = 0;
>>
>> @@ -338,18 +341,25 @@ static int cuda_device_create(AVHWDeviceContext
>> *device_ctx,
>> if (ret < 0)
>> goto error;
>>
>> - ret = CHECK_CU(cu->cuDeviceGet(&cu_device, device_idx));
>> + ret = CHECK_CU(cu->cuDeviceGet(&hwctx->cuda_device,
>> device_idx));
>> if (ret < 0)
>> goto error;
>>
>> - ret = CHECK_CU(cu->cuCtxCreate(&hwctx->cuda_ctx,
>> CU_CTX_SCHED_BLOCKING_SYNC, cu_device));
>> + hwctx->flags = flags;
>> +
>> + if (flags == DCF_CREATE_CONTEXT)
>> + ret = CHECK_CU(cu->cuCtxCreate(&hwctx->cuda_ctx,
>> CU_CTX_SCHED_BLOCKING_SYNC, hwctx->cuda_device));
>> + else
>> + ret = CHECK_CU(cu->cuDevicePrimaryCtxRetain(&hwctx-
>>> cuda_ctx, hwctx->cuda_device));
>> +
>> if (ret < 0)
>> goto error;
>>
>> // Setting stream to NULL will make functions automatically use
>> the default CUstream
>> hwctx->stream = NULL;
>>
>> - CHECK_CU(cu->cuCtxPopCurrent(&dummy));
>> + if (flags == DCF_CREATE_CONTEXT)
>> + CHECK_CU(cu->cuCtxPopCurrent(&dummy));
>>
>> hwctx->internal->is_allocated = 1;
>>
>> diff --git a/libavutil/hwcontext_cuda.h b/libavutil/hwcontext_cuda.h
>> index 81a0552cab..bab5eefe54 100644
>> --- a/libavutil/hwcontext_cuda.h
>> +++ b/libavutil/hwcontext_cuda.h
>> @@ -34,6 +34,11 @@
>> * AVBufferRefs whose data pointer is a CUdeviceptr.
>> */
>>
>> +enum AVCUDADeviceContextFlags {
>> + DCF_CREATE_CONTEXT = 0,
>> + DCF_USE_PRIMARY_CONTEXT = 1
>> +};
>>
>> I'd only define a flag for the new behavior. If it's not set, keep
>> old
>> behavior.
>>
>>
>> typedef struct AVCUDADeviceContextInternal
>> AVCUDADeviceContextInternal;
>>
>> /**
>> @@ -43,6 +48,8 @@ typedef struct AVCUDADeviceContext {
>> CUcontext cuda_ctx;
>> CUstream stream;
>> AVCUDADeviceContextInternal *internal;
>> + CUdevice cuda_device;
>>
>> Can't one just call cuCtxGetDevice on the context to get the device?
>>
>>
>> + enum AVCUDADeviceContextFlags flags;
>>
>> The device_create/av_hwdevice_ctx_create function already has a (at
>> the
>> moment unused) flags parameter. So there should be no need to add
>> this here.
>> If need be, the information should be stored in
>> AVCUDADeviceContextInternal instead.
>>
>>
>> } AVCUDADeviceContext;
>>
>>
>> Also needs configure updated for the higher ffnvcodec version that's
>> required after this patch, and probably deserved a lavu micro bump.
>>
>>
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