On 04/08/2011 05:40 PM, Marko Ristola wrote:
> Avoid unnecessary DVB TS 188 sized packet copying from DMA buffer into stack.
> Backtrack one 188 sized packet just after some garbage bytes when possible.
> This obsoletes patch https://patchwork.kernel.org/patch/118147/
>
> Signed-off-by: Marko Ristola marko.rist...@kolumbus.fi
Did you intentionally send a version that doesn't use likely()? Anyway,
those optimizations can still be done in an incremental patch.
Acked-by: Andreas Oberritter <o...@linuxtv.org>
> diff --git a/drivers/media/dvb/dvb-core/dvb_demux.c
> b/drivers/media/dvb/dvb-core/dvb_demux.c
> index 4a88a3e..faa3671 100644
> --- a/drivers/media/dvb/dvb-core/dvb_demux.c
> +++ b/drivers/media/dvb/dvb-core/dvb_demux.c
> @@ -478,97 +478,94 @@ void dvb_dmx_swfilter_packets(struct dvb_demux *demux,
> const u8 *buf,
>
> EXPORT_SYMBOL(dvb_dmx_swfilter_packets);
>
> -void dvb_dmx_swfilter(struct dvb_demux *demux, const u8 *buf, size_t count)
> +static inline int find_next_packet(const u8 *buf, int pos, size_t count,
> + const int pktsize)
> {
> - int p = 0, i, j;
> + int start = pos, lost;
>
> - spin_lock(&demux->lock);
> -
> - if (demux->tsbufp) {
> - i = demux->tsbufp;
> - j = 188 - i;
> - if (count < j) {
> - memcpy(&demux->tsbuf[i], buf, count);
> - demux->tsbufp += count;
> - goto bailout;
> - }
> - memcpy(&demux->tsbuf[i], buf, j);
> - if (demux->tsbuf[0] == 0x47)
> - dvb_dmx_swfilter_packet(demux, demux->tsbuf);
> - demux->tsbufp = 0;
> - p += j;
> + while (pos < count) {
> + if (buf[pos] == 0x47 ||
> + (pktsize == 204 && buf[pos] == 0xB8))
> + break;
> + pos++;
> }
>
> - while (p < count) {
> - if (buf[p] == 0x47) {
> - if (count - p >= 188) {
> - dvb_dmx_swfilter_packet(demux, &buf[p]);
> - p += 188;
> - } else {
> - i = count - p;
> - memcpy(demux->tsbuf, &buf[p], i);
> - demux->tsbufp = i;
> - goto bailout;
> - }
> - } else
> - p++;
> + lost = pos - start;
> + if (lost) {
> + /* This garbage is part of a valid packet? */
> + int backtrack = pos - pktsize;
> + if (backtrack >= 0 && (buf[backtrack] == 0x47 ||
> + (pktsize == 204 && buf[backtrack] == 0xB8)))
> + return backtrack;
> }
>
> -bailout:
> - spin_unlock(&demux->lock);
> + return pos;
> }
>
> -EXPORT_SYMBOL(dvb_dmx_swfilter);
> -
> -void dvb_dmx_swfilter_204(struct dvb_demux *demux, const u8 *buf, size_t
> count)
> +/* Filter all pktsize= 188 or 204 sized packets and skip garbage. */
> +static inline void _dvb_dmx_swfilter(struct dvb_demux *demux, const u8 *buf,
> + size_t count, const int pktsize)
> {
> int p = 0, i, j;
> - u8 tmppack[188];
> + const u8 *q;
>
> spin_lock(&demux->lock);
>
> - if (demux->tsbufp) {
> + if (demux->tsbufp) { /* tsbuf[0] is now 0x47. */
> i = demux->tsbufp;
> - j = 204 - i;
> + j = pktsize - i;
> if (count < j) {
> memcpy(&demux->tsbuf[i], buf, count);
> demux->tsbufp += count;
> goto bailout;
> }
> memcpy(&demux->tsbuf[i], buf, j);
> - if ((demux->tsbuf[0] == 0x47) || (demux->tsbuf[0] == 0xB8)) {
> - memcpy(tmppack, demux->tsbuf, 188);
> - if (tmppack[0] == 0xB8)
> - tmppack[0] = 0x47;
> - dvb_dmx_swfilter_packet(demux, tmppack);
> - }
> + if (demux->tsbuf[0] == 0x47) /* double check */
> + dvb_dmx_swfilter_packet(demux, demux->tsbuf);
> demux->tsbufp = 0;
> p += j;
> }
>
> - while (p < count) {
> - if ((buf[p] == 0x47) || (buf[p] == 0xB8)) {
> - if (count - p >= 204) {
> - memcpy(tmppack, &buf[p], 188);
> - if (tmppack[0] == 0xB8)
> - tmppack[0] = 0x47;
> - dvb_dmx_swfilter_packet(demux, tmppack);
> - p += 204;
> - } else {
> - i = count - p;
> - memcpy(demux->tsbuf, &buf[p], i);
> - demux->tsbufp = i;
> - goto bailout;
> - }
> - } else {
> - p++;
> + while (1) {
> + p = find_next_packet(buf, p, count, pktsize);
> + if (p >= count)
> + break;
> + if (count - p < pktsize)
> + break;
> +
> + q = &buf[p];
> +
> + if (pktsize == 204 && (*q == 0xB8)) {
> + memcpy(demux->tsbuf, q, 188);
> + demux->tsbuf[0] = 0x47;
> + q = demux->tsbuf;
> }
> + dvb_dmx_swfilter_packet(demux, q);
> + p += pktsize;
> + }
> +
> + i = count - p;
> + if (i) {
> + memcpy(demux->tsbuf, &buf[p], i);
> + demux->tsbufp = i;
> + if (pktsize == 204 && demux->tsbuf[0] == 0xB8)
> + demux->tsbuf[0] = 0x47;
> }
>
> bailout:
> spin_unlock(&demux->lock);
> }
>
> +void dvb_dmx_swfilter(struct dvb_demux *demux, const u8 *buf, size_t count)
> +{
> + _dvb_dmx_swfilter(demux, buf, count, 188);
> +}
> +EXPORT_SYMBOL(dvb_dmx_swfilter);
> +
> +void dvb_dmx_swfilter_204(struct dvb_demux *demux, const u8 *buf, size_t
> count)
> +{
> + _dvb_dmx_swfilter(demux, buf, count, 204);
> +}
> EXPORT_SYMBOL(dvb_dmx_swfilter_204);
>
> static struct dvb_demux_filter *dvb_dmx_filter_alloc(struct dvb_demux *demux)
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