On 2023-09-05 05:48, Takashi Yano via Cygwin-apps wrote:
On Tue, 5 Sep 2023 12:37:28 +0100
Jon Turney wrote:
On 05/09/2023 10:28, Takashi Yano wrote:
Previous wait time of 100msec is too long if application specifies
smaller buffer. With this patch, the wait time is reduced to 1msec.
I don't really have the context to understand this change, but it seems
to me the obvious questions to ask are:
Are there negative consequences of making this wait much smaller (i.e.
lots more CPU spent busy-waiting?)
Your comment seems to imply that the wait time should be proportional to
the buffer size and sample rate?
---
winsup/cygwin/fhandler/dsp.cc | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/winsup/cygwin/fhandler/dsp.cc b/winsup/cygwin/fhandler/dsp.cc
index e872aa08c..00f2bab69 100644
--- a/winsup/cygwin/fhandler/dsp.cc
+++ b/winsup/cygwin/fhandler/dsp.cc
@@ -931,8 +931,8 @@ fhandler_dev_dsp::Audio_in::waitfordata ()
set_errno (EAGAIN);
return false;
}
- debug_printf ("100ms");
- switch (cygwait (100))
+ debug_printf ("1ms");
+ switch (cygwait (1))
{
case WAIT_SIGNALED:
if (!_my_tls.call_signal_handler ())
The code around the modification is as follows.
while (!Qisr2app_->recv (&pHdr))
{
if (fh->is_nonblocking ())
{
set_errno (EAGAIN);
return false;
}
debug_printf ("1ms");
switch (cygwait (1))
{
case WAIT_SIGNALED:
if (!_my_tls.call_signal_handler ())
{
set_errno (EINTR);
return false;
}
break;
case WAIT_CANCELED:
pthread::static_cancel_self ();
/*NOTREACHED*/
default:
break;
}
}
while loop is very short, so almost all the time in the loop
is consumed by cygwait() even with wait time of 1msec.
Theoretically, the CPU gets 100 times load, however, it is
too small to care the CPU load.
Our sound and synth guy *Achim* would probably be the best person to review and
comment!
I know Windows historically had to add support for a 1ms MultiMedia Timer, to
avoid A/V artifacts, as ms really matter for audio delay and phasing, when
peer-to-peer digital media exchange first became popular, and it is enabled for
the system by Meinberg's Windows ntpd daemon, which needs it for network timing.
--
Take care. Thanks, Brian Inglis Calgary, Alberta, Canada
La perfection est atteinte Perfection is achieved
non pas lorsqu'il n'y a plus rien à ajouter not when there is no more to add
mais lorsqu'il n'y a plus rien à retirer but when there is no more to cut
-- Antoine de Saint-Exupéry
