* [PATCH] Speed up DVB TS stream delivery from DMA buffer into dvb-core's buffer
@ 2011-04-08 15:40 Marko Ristola
2011-04-08 19:37 ` Marko Ristola
2011-04-10 12:10 ` Andreas Oberritter
0 siblings, 2 replies; 4+ messages in thread
From: Marko Ristola @ 2011-04-08 15:40 UTC (permalink / raw)
To: Andreas Oberritter; +Cc: Mauro Carvalho Chehab, Linux Media Mailing List
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.ristola@kolumbus.fi
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)
^ permalink raw reply related [flat|nested] 4+ messages in thread* Re: [PATCH] Speed up DVB TS stream delivery from DMA buffer into dvb-core's buffer
2011-04-08 15:40 [PATCH] Speed up DVB TS stream delivery from DMA buffer into dvb-core's buffer Marko Ristola
@ 2011-04-08 19:37 ` Marko Ristola
2011-04-10 12:28 ` Andreas Oberritter
2011-04-10 12:10 ` Andreas Oberritter
1 sibling, 1 reply; 4+ messages in thread
From: Marko Ristola @ 2011-04-08 19:37 UTC (permalink / raw)
To: Marko Ristola
Cc: Andreas Oberritter, Mauro Carvalho Chehab,
Linux Media Mailing List
Here is some statistics without likely and with likely functions.
It seems that using likely() gives better performance with Phenom I too.
% Plain knl % No likely % With likely %
dvb_ringbuffer_write 5,9 62,8 8,7 81,3 5,7 79,2
dvb_dmx_swfilter_packet 1,2 12,8 0,7 6,5 0,8 11,1
dvb_dmx_swfilter_204 2,3 24,5 1,3 12,1 0,7 9,7
Here "Plain knl %" is "perf top -d 30" percentage.
24,5 12,1 and 9,7 are percentages without a patch, with basic patch
and last is with "likely" functions using patch.
Regards,
Marko Ristola
08.04.2011 18:40, Marko Ristola kirjoitti:
> 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.ristola@kolumbus.fi
> 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);
>
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] Speed up DVB TS stream delivery from DMA buffer into dvb-core's buffer
2011-04-08 19:37 ` Marko Ristola
@ 2011-04-10 12:28 ` Andreas Oberritter
0 siblings, 0 replies; 4+ messages in thread
From: Andreas Oberritter @ 2011-04-10 12:28 UTC (permalink / raw)
To: Marko Ristola; +Cc: Mauro Carvalho Chehab, Linux Media Mailing List
On 04/08/2011 09:37 PM, Marko Ristola wrote:
>
> Here is some statistics without likely and with likely functions.
>
> It seems that using likely() gives better performance with Phenom I too.
I'm not sure whether that's the right conclusion. See below.
> % Plain knl % No likely % With likely %
> dvb_ringbuffer_write 5,9 62,8 8,7 81,3 5,7 79,2
> dvb_dmx_swfilter_packet 1,2 12,8 0,7 6,5 0,8 11,1
> dvb_dmx_swfilter_204 2,3 24,5 1,3 12,1 0,7 9,7
>
>
> Here "Plain knl %" is "perf top -d 30" percentage.
> 24,5 12,1 and 9,7 are percentages without a patch, with basic patch
> and last is with "likely" functions using patch.
The varying ratio between dvb_ringbuffer_write and
dvb_dmx_swfilter_packet, which haven't been modified by the patch, seems
to indicate that the numbers were influenced by other activities on the
system or by the data used during the tests. 8,7% for
dvb_ringbuffer_write in test #2 could also indicate a higher data rate
than in #1 and #3.
However, adding likely() certainly won't do any harm. Feel free to send
an incremental patch.
Regards,
Andreas
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] Speed up DVB TS stream delivery from DMA buffer into dvb-core's buffer
2011-04-08 15:40 [PATCH] Speed up DVB TS stream delivery from DMA buffer into dvb-core's buffer Marko Ristola
2011-04-08 19:37 ` Marko Ristola
@ 2011-04-10 12:10 ` Andreas Oberritter
1 sibling, 0 replies; 4+ messages in thread
From: Andreas Oberritter @ 2011-04-10 12:10 UTC (permalink / raw)
To: Marko Ristola; +Cc: Mauro Carvalho Chehab, Linux Media Mailing List
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.ristola@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 <obi@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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^ permalink raw reply [flat|nested] 4+ messages in thread
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2011-04-08 15:40 [PATCH] Speed up DVB TS stream delivery from DMA buffer into dvb-core's buffer Marko Ristola
2011-04-08 19:37 ` Marko Ristola
2011-04-10 12:28 ` Andreas Oberritter
2011-04-10 12:10 ` Andreas Oberritter
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