[vlc-devel] [PATCH 1/1] packetizer: flac: reduce memory allocations

[Tristan Matthews]

On Fri, Nov 21, 2014 at 4:03 AM, Jean-Baptiste Kempf <jb at videolan.org>
wrote:

> Do you see a CPU difference?
>

Not a huge one in the grand scheme of things, but for a given file, with
this patch I get:
15 calls to realloc * 234 instructions per call + and 1 call to free * 96
instructions per call = 3606 instructions
VS.
4872 calls to malloc * 206 instructions per call +  4872 calls to free * 96
instructions per call = 1607760 instructions

but it only saves about 0.01% CPU overall.

-t


>
> On 21 Nov, Tristan Matthews wrote :
> > ---
> >  modules/packetizer/flac.c | 21 ++++++++++++++-------
> >  1 file changed, 14 insertions(+), 7 deletions(-)
> >
> > diff --git a/modules/packetizer/flac.c b/modules/packetizer/flac.c
> > index ecf854f..25f1957 100644
> > --- a/modules/packetizer/flac.c
> > +++ b/modules/packetizer/flac.c
> > @@ -90,6 +90,8 @@ struct decoder_sys_t
> >      size_t i_frame_size;
> >      uint16_t crc;
> >      unsigned int i_rate, i_channels, i_bits_per_sample;
> > +    size_t i_buf;
> > +    uint8_t *p_buf;
> >  };
> >
> >  static const int pi_channels_maps[9] =
> > @@ -603,19 +605,21 @@ static block_t *Packetize(decoder_t *p_dec,
> block_t **pp_block)
> >      {
> >          /* Calculate the initial CRC for the minimal frame size,
> >           * We'll update it as we look for the next start code. */
> > -        uint8_t *buf = malloc(p_sys->i_frame_size);
> > -        if (!buf)
> > -            return NULL;
> > +        if (p_sys->i_buf < p_sys->i_frame_size)
> > +        {
> > +            p_sys->p_buf = realloc(p_sys->p_buf, p_sys->i_frame_size);
> > +            if (!p_sys->p_buf)
> > +                return NULL;
> > +            p_sys->i_buf = p_sys->i_frame_size;
> > +        }
> >
> > -        if (block_PeekOffsetBytes(&p_sys->bytestream, 0, buf,
> p_sys->i_frame_size)) {
> > -            free(buf);
> > +        if (block_PeekOffsetBytes(&p_sys->bytestream, 0, p_sys->p_buf,
> p_sys->i_frame_size)) {
> >              return NULL;
> >          }
> >
> >          uint16_t crc = 0;
> >          for (unsigned i = 0; i < p_sys->i_frame_size; i++)
> > -            crc = flac_crc16(crc, buf[i]);
> > -        free(buf);
> > +            crc = flac_crc16(crc, p_sys->p_buf[i]);
> >          p_sys->crc = crc;
> >
> >          /* Check if next expected frame contains the sync word */
> > @@ -752,6 +756,8 @@ static int Open(vlc_object_t *p_this)
> >      p_sys->i_state       = STATE_NOSYNC;
> >      p_sys->b_stream_info = false;
> >      p_sys->i_pts         = VLC_TS_INVALID;
> > +    p_sys->i_buf         = 0;
> > +    p_sys->p_buf         = NULL;
> >      block_BytestreamInit(&p_sys->bytestream);
> >
> >      /* */
> > @@ -773,5 +779,6 @@ static void Close(vlc_object_t *p_this)
> >
> >      es_format_Clean(&p_dec->fmt_out);
> >      block_BytestreamRelease(&p_sys->bytestream);
> > +    free(p_sys->p_buf);
> >      free(p_sys);
> >  }
> > --
> > 1.9.3
> >
> > _______________________________________________
> > vlc-devel mailing list
> > To unsubscribe or modify your subscription options:
> > https://mailman.videolan.org/listinfo/vlc-devel
>
> --
> With my kindest regards,
>
> --
> Jean-Baptiste Kempf
> http://www.jbkempf.com/ - +33 672 704 734
> Sent from my Electronic Device
> _______________________________________________
> vlc-devel mailing list
> To unsubscribe or modify your subscription options:
> https://mailman.videolan.org/listinfo/vlc-devel
>
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