Hi,
Le lundi 03 juin 2019 à 18:37 +0200, Jernej Škrabec a écrit :
> Dne ponedeljek, 03. junij 2019 ob 14:23:28 CEST je Maxime Ripard napisal(a):
> > On Thu, May 30, 2019 at 11:15:16PM +0200, Jernej Skrabec wrote:
> > > H264 decoder driver preallocated pretty big worst case mv col buffer
> > > pool. It turns out that pool is most of the time much bigger than it
> > > needs to be.
> > >
> > > Solution implemented here is to allocate memory only if capture buffer
> > > is actually used and only as much as it is really necessary.
> > >
> > > This is also preparation for 4K video decoding support, which will be
> > > implemented later.
> >
> > What is it doing exactly to prepare for 4k?
>
> Well, with that change 4K videos can be actually watched with 256 MiB CMA
> pool, but I can drop this statement in next version.
>
> I concentrated on 256 MiB CMA pool, because it's maximum memory size supported
> by older VPU versions, but I think they don't support 4K decoding. I don't
> have them, so I can't test that hypothesis.
I think it's a fair goal to try and optimize the CMA pool usage, maybe
it should be presented as that and I guess it's fine to connect that to
4K decoding if you like :)
Either way, I think we should have per-codec framework callbacks for
these kinds of things.
Cheers,
Paul
> > > Signed-off-by: Jernej Skrabec <jernej.skrabec@xxxxxxxx>
> > > ---
> > >
> > > drivers/staging/media/sunxi/cedrus/cedrus.h | 4 -
> > > .../staging/media/sunxi/cedrus/cedrus_h264.c | 81 +++++++------------
> > > 2 files changed, 28 insertions(+), 57 deletions(-)
> > >
> > > diff --git a/drivers/staging/media/sunxi/cedrus/cedrus.h
> > > b/drivers/staging/media/sunxi/cedrus/cedrus.h index
> > > 16c1bdfd243a..fcbbbef65494 100644
> > > --- a/drivers/staging/media/sunxi/cedrus/cedrus.h
> > > +++ b/drivers/staging/media/sunxi/cedrus/cedrus.h
> > > @@ -106,10 +106,6 @@ struct cedrus_ctx {
> > >
> > > union {
> > >
> > > struct {
> > >
> > > - void *mv_col_buf;
> > > - dma_addr_t mv_col_buf_dma;
> > > - ssize_t mv_col_buf_field_size;
> > > - ssize_t mv_col_buf_size;
> > >
> > > void *pic_info_buf;
> > > dma_addr_t pic_info_buf_dma;
> > > void *neighbor_info_buf;
> > >
> > > diff --git a/drivers/staging/media/sunxi/cedrus/cedrus_h264.c
> > > b/drivers/staging/media/sunxi/cedrus/cedrus_h264.c index
> > > b2290f98d81a..758fd0049e8f 100644
> > > --- a/drivers/staging/media/sunxi/cedrus/cedrus_h264.c
> > > +++ b/drivers/staging/media/sunxi/cedrus/cedrus_h264.c
> > > @@ -54,17 +54,14 @@ static void cedrus_h264_write_sram(struct cedrus_dev
> > > *dev,>
> > > cedrus_write(dev, VE_AVC_SRAM_PORT_DATA, *buffer++);
> > >
> > > }
> > >
> > > -static dma_addr_t cedrus_h264_mv_col_buf_addr(struct cedrus_ctx *ctx,
> > > - unsigned int
> position,
> > > +static dma_addr_t cedrus_h264_mv_col_buf_addr(struct cedrus_buffer *buf,
> > >
> > > unsigned int
> field)
> > >
> > > {
> > >
> > > - dma_addr_t addr = ctx->codec.h264.mv_col_buf_dma;
> > > -
> > > - /* Adjust for the position */
> > > - addr += position * ctx->codec.h264.mv_col_buf_field_size * 2;
> > > + dma_addr_t addr = buf->extra_buf_dma;
> > >
> > > /* Adjust for the field */
> > >
> > > - addr += field * ctx->codec.h264.mv_col_buf_field_size;
> > > + if (field)
> > > + addr += buf->extra_buf_size / 2;
> > >
> > > return addr;
> > >
> > > }
> > >
> > > @@ -76,7 +73,6 @@ static void cedrus_fill_ref_pic(struct cedrus_ctx *ctx,
> > >
> > > struct cedrus_h264_sram_ref_pic
> *pic)
> > >
> > > {
> > >
> > > struct vb2_buffer *vbuf = &buf->m2m_buf.vb.vb2_buf;
> > >
> > > - unsigned int position = buf->codec.h264.position;
> > >
> > > pic->top_field_order_cnt = cpu_to_le32(top_field_order_cnt);
> > > pic->bottom_field_order_cnt = cpu_to_le32(bottom_field_order_cnt);
> > >
> > > @@ -84,10 +80,8 @@ static void cedrus_fill_ref_pic(struct cedrus_ctx *ctx,
> > >
> > > pic->luma_ptr = cpu_to_le32(cedrus_buf_addr(vbuf, &ctx->dst_fmt,
> 0));
> > > pic->chroma_ptr = cpu_to_le32(cedrus_buf_addr(vbuf, &ctx->dst_fmt,
> 1));
> > > - pic->mv_col_top_ptr =
> > > - cpu_to_le32(cedrus_h264_mv_col_buf_addr(ctx, position,
> 0));
> > > - pic->mv_col_bot_ptr =
> > > - cpu_to_le32(cedrus_h264_mv_col_buf_addr(ctx, position,
> 1));
> > > + pic->mv_col_top_ptr = cpu_to_le32(cedrus_h264_mv_col_buf_addr(buf,
> 0));
> > > + pic->mv_col_bot_ptr = cpu_to_le32(cedrus_h264_mv_col_buf_addr(buf,
> 1));
> > > }
> > >
> > > static void cedrus_write_frame_list(struct cedrus_ctx *ctx,
> > >
> > > @@ -142,6 +136,28 @@ static void cedrus_write_frame_list(struct cedrus_ctx
> > > *ctx,>
> > > output_buf = vb2_to_cedrus_buffer(&run->dst->vb2_buf);
> > > output_buf->codec.h264.position = position;
> > >
> > > + if (!output_buf->extra_buf_size) {
> > > + const struct v4l2_ctrl_h264_sps *sps = run->h264.sps;
> > > + unsigned int field_size;
> > > +
> > > + field_size = DIV_ROUND_UP(ctx->src_fmt.width, 16) *
> > > + DIV_ROUND_UP(ctx->src_fmt.height, 16) * 16;
> > > + if (!(sps->flags &
> V4L2_H264_SPS_FLAG_DIRECT_8X8_INFERENCE))
> > > + field_size = field_size * 2;
> > > + if (!(sps->flags & V4L2_H264_SPS_FLAG_FRAME_MBS_ONLY))
> > > + field_size = field_size * 2;
> > > +
> > > + output_buf->extra_buf_size = field_size * 2;
> > > + output_buf->extra_buf =
> > > + dma_alloc_coherent(dev->dev,
> > > + output_buf-
> > extra_buf_size,
> > > + &output_buf-
> > extra_buf_dma,
> > > + GFP_KERNEL);
> > > +
> > > + if (!output_buf->extra_buf)
> > > + output_buf->extra_buf_size = 0;
> > > + }
> > > +
> >
> > That also means that instead of allocating that buffer exactly once,
> > you now allocate it for each output buffer?
>
> It's not completely the same. I'm allocating multiple times, yes, but much
> smaller chunks and only if needed.
>
> Still, this slight overhead happens only when buffer is used for the first time.
> When buffer is reused, this MV buffer is also reused.
>
> > I guess that it will cleaned up by your previous patch at
> > buffer_cleanup time, so after it's no longer a reference frame?
>
> Yes, it will be deallocated in buffer_cleanup, but only after capture buffers
> are freed, which usually happens when device file descriptor is closed.
>
> Buffers which holds reference frames are later reused, together with it's MV
> buffer, so there's no overhead.
>
> > What is the average memory usage before, and after that change during
> > a playback, and what is the runtime cost of doing it multiple times
> > instead of once?
>
> As I already said, overhead is present only when buffer is used for the first
> time, which is not ideal, but allows to calculate minimal buffer size needed
> and even doesn't allocate anything if capture buffer is not used at all.
>
> I didn't collect any exact numbers, but with this change I can play H264 and
> HEVC (with similar modification) 4K video samples with 256 MiB CMA pool.
> Without this change, it's not really possible. You can argue "but what if 4K
> video use 16 reference frames", then yes, only solution is to increase CMA
> pool, but why reserve extra memory which will never be used?
>
> I've been using this optimization for past ~6 month with no issues noticed. If
> you feel better, I can change this to be a bit conservative and allocate MV
> buffer when buffer_init is called. This will consume a bit more memory as SPS is
> not available at that time (worst case buffer size estimation), but it still
> won't allocate MV buffers for unallocated capture frames.
>
> Best regards,
> Jernej
>
>
