[Bluez-devel] PATCH2/2: bluez-utils - avoid-unnecessary-polls

[Bluez-devel] PATCH2/2: bluez-utils - avoid-unnecessary-polls

[Kai Vehmanen]

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Hello again,

here's the second patch to ALSA A2DP plugin in bluez-utils
(see my previous mail).

This patch changes the worker thread poll timeout to be 
calculated according to application chosen period size. 
This allows to decrease the CPU load significantly for those 
applications that do not require an ultra small period
size. Without the patch (poll timeout of 1msec), the system 
call load is pretty heavy...

Br,
-- 
first.surname@nokia.com (Kai Vehmanen)

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diff -ruN bluez-utils.orig/audio/pcm_bluetooth.c bluez-utils/audio/pcm_bluetooth.c
--- bluez-utils.orig/audio/pcm_bluetooth.c	2007-10-12 15:07:40.000000000 +0300
+++ bluez-utils/audio/pcm_bluetooth.c	2007-10-12 15:04:58.000000000 +0300
@@ -168,12 +168,17 @@
 	double period_time;
 	struct timeval start;
 	struct pollfd fds[2];
+	int poll_timeout;
 
 	fds[0] = data->server;
 	fds[1] = data->stream;
 
 	prev_periods = 0;
 	period_time = 1000000.0 * data->io.period_size / data->io.rate;
+	if (period_time > (int)(MIN_PERIOD_TIME * 1000))
+		poll_timeout = (int)(period_time / 1000.0f);
+	else
+		poll_timeout = MIN_PERIOD_TIME;
 
 	gettimeofday(&start, 0);
 
@@ -214,7 +219,8 @@
 		}
 
 iter_sleep:
-		ret = poll(fds, 2, MIN_PERIOD_TIME);
+		/* sleep up to one period interval */
+		ret = poll(fds, 2, poll_timeout);
 		if (ret < 0) {
 			SNDERR("poll error: %s (%d)", strerror(errno), errno);
 			if (errno != EINTR)

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Re: [Bluez-devel] PATCH2/2: bluez-utils - avoid-unnecessary-polls

[Luiz Augusto von Dentz]

Hi Kai,

On 10/12/07, Kai Vehmanen <kai.vehmanen@nokia.com> wrote:
> Hello again,
>
> here's the second patch to ALSA A2DP plugin in bluez-utils
> (see my previous mail).
>
> This patch changes the worker thread poll timeout to be
> calculated according to application chosen period size.
> This allows to decrease the CPU load significantly for those
> applications that do not require an ultra small period
> size. Without the patch (poll timeout of 1msec), the system
> call load is pretty heavy...

This was done before but I guess for some reason I don't remember
now we remove it in favor of fixed timeout. Thought we should
reconsider it if it has a good impact on CPU load.

-- =

Luiz Augusto von Dentz
Engenheiro de Computa=E7=E3o

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