[vlc-devel] [PATCH 2/2] codec: dav1d: limit automatic frame thread count

[Alexandre Janniaux]

Hi,

On Fri, Nov 20, 2020 at 07:57:56AM +0100, Steve Lhomme wrote:
> It would be OK to limit that way in 3.0.
>
> In 4.0, with push, the pool can be allocated in the Open of the decoder and
> if it fails we can allows loop to find the number of threads that work.
>
> IMO if someone has 64 threads and 256 GB of RAM to decode/transcode as fast
> as possible, there's no reason to limit the decoding speed artificially.
>
> This is less true for lavc as we only know the chroma to allocate after the
> decoder is started.

However, we might want to cap this to 64 since that's the
high limit of picture pools currently.

Regards,
--
Alexandre Janniaux
Videolabs

> On 2020-11-19 17:15, Marvin Scholz wrote:
> > Without this limit, on a processor with many cores it would use
> > so many frame threads that it would fail picture pool allocation.
> >
> > Fix #25190
> > ---
> >   modules/codec/dav1d.c | 2 +-
> >   1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/modules/codec/dav1d.c b/modules/codec/dav1d.c
> > index dcb09213186..8611b0cdfe9 100644
> > --- a/modules/codec/dav1d.c
> > +++ b/modules/codec/dav1d.c
> > @@ -396,7 +396,7 @@ static int OpenDecoder(vlc_object_t *p_this)
> >           p_sys->s.n_tile_threads = VLC_CLIP(vlc_GetCPUCount(), 1, 4);
> >       p_sys->s.n_frame_threads = var_InheritInteger(p_this, "dav1d-thread-frames");
> >       if (p_sys->s.n_frame_threads == 0)
> > -        p_sys->s.n_frame_threads = __MAX(1, vlc_GetCPUCount());
> > +        p_sys->s.n_frame_threads = VLC_CLIP(vlc_GetCPUCount(), 1, 16);
> >       p_sys->s.allocator.cookie = dec;
> >       p_sys->s.allocator.alloc_picture_callback = NewPicture;
> >       p_sys->s.allocator.release_picture_callback = FreePicture;
> > --
> > 2.24.3 (Apple Git-128)
> >
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