[libav-devel] [PATCH v4] qsvvpp: Fix to perform full init only when needed

Mark Thompson sw at jkqxz.net
Wed Jul 18 00:48:00 CEST 2018


On 17/07/18 17:07, Maxym Dmytrychenko wrote:
> Not used VPP sessions, like for hwupload/hwdownload handling,
> can increase CPU utilization and this patch fixes it.
> thank you,Joe, for the contribution.
> 
> Signed-off-by: Maxym Dmytrychenko <maxim.d33 at gmail.com>
> ---
>  libavutil/hwcontext_qsv.c | 38 +++++++++++++++++++++++++++++---------
>  1 file changed, 29 insertions(+), 9 deletions(-)
> 
> diff --git a/libavutil/hwcontext_qsv.c b/libavutil/hwcontext_qsv.c
> index b3eb4a3ea..390c3aac4 100644
> --- a/libavutil/hwcontext_qsv.c
> +++ b/libavutil/hwcontext_qsv.c
> @@ -18,6 +18,7 @@
>  
>  #include <stdint.h>
>  #include <string.h>
> +#include <stdatomic.h>
>  
>  #include <mfx/mfxvideo.h>
>  
> @@ -56,7 +57,9 @@ typedef struct QSVDeviceContext {
>  
>  typedef struct QSVFramesContext {
>      mfxSession session_download;
> +    atomic_int session_download_init;
>      mfxSession session_upload;
> +    atomic_int session_upload_init;
>  
>      AVBufferRef *child_frames_ref;
>      mfxFrameSurface1 *surfaces_internal;
> @@ -146,13 +149,15 @@ static void qsv_frames_uninit(AVHWFramesContext *ctx)
>          MFXVideoVPP_Close(s->session_download);
>          MFXClose(s->session_download);
>      }
> -    s->session_download = NULL;
> +    s->session_download      = NULL;
> +    s->session_download_init = 0;
>  
>      if (s->session_upload) {
>          MFXVideoVPP_Close(s->session_upload);
>          MFXClose(s->session_upload);
>      }
> -    s->session_upload = NULL;
> +    s->session_upload      = NULL;
> +    s->session_upload_init = 0;
>  
>      av_freep(&s->mem_ids);
>      av_freep(&s->surface_ptrs);
> @@ -535,13 +540,10 @@ static int qsv_frames_init(AVHWFramesContext *ctx)
>              s->mem_ids[i] = frames_hwctx->surfaces[i].Data.MemId;
>      }
>  
> -    ret = qsv_init_internal_session(ctx, &s->session_download, 0);
> -    if (ret < 0)
> -        return ret;
> -
> -    ret = qsv_init_internal_session(ctx, &s->session_upload, 1);
> -    if (ret < 0)
> -        return ret;
> +    s->session_download      = NULL;
> +    s->session_upload        = NULL;
> +    s->session_download_init = 0;
> +    s->session_upload_init   = 0;
>  
>      return 0;
>  }
> @@ -741,6 +743,15 @@ static int qsv_transfer_data_from(AVHWFramesContext *ctx, AVFrame *dst,
>      mfxSyncPoint sync = NULL;
>      mfxStatus err;
>  
> +    while (!s->session_download_init && !s->session_download) {
> +	if (atomic_fetch_add(&s->session_download_init, 1) == 0) {
> +            qsv_init_internal_session(ctx, &s->session_download, 0);
> +        }
> +	else {
> +            av_usleep(1);

This races - consider what happens if the other thread is preempted for more than 1┬Ás, or if the initialisation itself takes more than that long.

You need to actually do some synchronisation here (e.g. with a 'once' variable) - with only atomic flags there is no way to guarantee that the other thread has finished unless you spin, which isn't acceptable.

> +        }
> +    }
> +
>      if (!s->session_download) {
>          if (s->child_frames_ref)
>              return qsv_transfer_data_child(ctx, dst, src);
> @@ -788,6 +799,15 @@ static int qsv_transfer_data_to(AVHWFramesContext *ctx, AVFrame *dst,
>      mfxSyncPoint sync = NULL;
>      mfxStatus err;
>  
> +    while (!s->session_upload_init && !s->session_upload) {
> +	if (atomic_fetch_add(&s->session_upload_init, 1) == 0) {
> +            qsv_init_internal_session(ctx, &s->session_upload, 1);
> +        }
> +	else {
> +            av_usleep(1);
> +        }
> +    }
> +
>      if (!s->session_upload) {
>          if (s->child_frames_ref)
>              return qsv_transfer_data_child(ctx, dst, src);
> 

Thanks,

- Mark


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