Re: [Asterisk-Dev] High resolution timers using POSIX clocks instead of zaptel
Gilad Ben-Yossef wrote: Derek Smithies wrote: Does anyone have some realworld experience on a recent machine & software timers to prove they are still a bad idea? Fact of life - on a 2.4 Linux kernel for x86 or PPC the timer resolution is 10ms (look for the HZ macro in /usr/src/linux/include/asm/param.h) That's simply not enough. Not enough for what? What do you need to do that 10ms resultion isn't enough? -SteveK ___ Asterisk-Dev mailing list Asterisk-Dev@lists.digium.com http://lists.digium.com/mailman/listinfo/asterisk-dev To UNSUBSCRIBE or update options visit: http://lists.digium.com/mailman/listinfo/asterisk-dev
Re: [Asterisk-Dev] High resolution timers using POSIX clocks instead of zaptel
Derek Smithies wrote: Does anyone have some realworld experience on a recent machine & software timers to prove they are still a bad idea? Fact of life - on a 2.4 Linux kernel for x86 or PPC the timer resolution is 10ms (look for the HZ macro in /usr/src/linux/include/asm/param.h) That's simply not enough. 2.6 is a whole different kettle of fish. Gilad -- Gilad Ben-Yossef <[EMAIL PROTECTED]> Codefidence. A name you can trust(tm) Web: http://codefidence.com | SIP: [EMAIL PROTECTED] IL: +972.9.8650475 ext. 201 | Fax:+972.9.8850643 US: +1.360.2275194 ext. 201 | Cel: +972.52.8260388 "I am Jack's Overwritten Stack Pointer" -- Hackers Club, the movie ___ Asterisk-Dev mailing list Asterisk-Dev@lists.digium.com http://lists.digium.com/mailman/listinfo/asterisk-dev To UNSUBSCRIBE or update options visit: http://lists.digium.com/mailman/listinfo/asterisk-dev
Re: [Asterisk-Dev] High resolution timers using POSIX clocks instead of zaptel
On Sat, 2005-05-28 at 10:56 +1200, Derek Smithies wrote: > Does anyone have some realworld experience on a recent machine & software > timers to prove they are still a bad idea? Anyone using ztdummy on a 2.6 kernel is using precisely the same software timers which drive the kernel's POSIX timer support. -- dwmw2 ___ Asterisk-Dev mailing list Asterisk-Dev@lists.digium.com http://lists.digium.com/mailman/listinfo/asterisk-dev To UNSUBSCRIBE or update options visit: http://lists.digium.com/mailman/listinfo/asterisk-dev
Re: [Asterisk-Dev] High resolution timers using POSIX clocks instead of zaptel
Hi, > >software timers are lacking. > > > > > > I think that is just narrow thinking. Steve's original link for why software timers are a bad idea was from 2002. Since then we have had fantastic improvements in a) cpu performance b) latency of the kernel - anyone tried the low latency kernel & software times? c) the overall kernel code. I think it is a reasonable question then: Are software timers still a bad idea? Does anyone have some realworld experience on a recent machine & software timers to prove they are still a bad idea? Derek -- Derek Smithies Ph.D. IndraNet Technologies Ltd. Email: [EMAIL PROTECTED] ph +64 3 365 6485 Web: http://www.indranet-technologies.com/ ___ Asterisk-Dev mailing list Asterisk-Dev@lists.digium.com http://lists.digium.com/mailman/listinfo/asterisk-dev To UNSUBSCRIBE or update options visit: http://lists.digium.com/mailman/listinfo/asterisk-dev
Re: [Asterisk-Dev] High resolution timers using POSIX clocks instead of zaptel
On May 27, 2005 12:32 pm, Tilghman Lesher wrote: > On Friday 27 May 2005 05:33, David Woodhouse wrote: > > Using zaptel just for a time source is silly. We should use POSIX > > timers instead. Here's a start, but I don't know how long it'll be > > before I can get to finish it, so I thought I'd post it here in the > > hope that someone else will pick it up. > > As noted here: > > http://lists.digium.com/pipermail/asterisk-users/2002-April/002072.html > > software timers are lacking. That link doesn't have *any* information whatsoever on why. 1000Hz should be trivial to generate on a PC. hell I was doing this back in the DOS days with the PIT. Granted things have changed a bit since then but I hardly think that a crystal oscillator on a PCI chipset *designed* to be as cheap as humanly possible is "great precision" as the link indicates. :-) -A. ___ Asterisk-Dev mailing list Asterisk-Dev@lists.digium.com http://lists.digium.com/mailman/listinfo/asterisk-dev To UNSUBSCRIBE or update options visit: http://lists.digium.com/mailman/listinfo/asterisk-dev
Re: [Asterisk-Dev] High resolution timers using POSIX clocks instead of zaptel
Tilghman Lesher wrote:
On Friday 27 May 2005 05:33, David Woodhouse wrote:
Using zaptel just for a time source is silly. We should use POSIX
timers instead. Here's a start, but I don't know how long it'll be
before I can get to finish it, so I thought I'd post it here in the
hope that someone else will pick it up.
As noted here:
http://lists.digium.com/pipermail/asterisk-users/2002-April/002072.html
software timers are lacking.
I think that is just narrow thinking.
app_conference works all day and week long, without any hardware
support. It also does it without posix timers. It just uses nanosleep
and gettimeofday.
You can make things go X times per second, with great accuracy over a
long period of time with just those tools. What you can't always do is
make sure that you don't have a period where you oversleep for a few ten
of milliseconds. But if you keep track of time, you can just do more
work when you do wake up.
i.e. in pseudo-code
do_something_n_times_per_second(func_t something, int n) {
long now, last, begin = getcurrentmillis();
last = begin;
for(;;) {
usleep(n);
time now = getcurrentmillis();
while(last < now) {
something();
last+=n;
}
}
}
where getcurrentmillis() can be based on gettimeofday, of course.
This will call something() 1000/n times per second. It might not be
spaced out so that it happens _exactly_ every n ms, but it will, over a
particular time period, happen 1000/n times per second.
If this runs in a real-time process, and the something() takes less than
n ms to run, it will happen very close to every n ms.
Of course, most things don't need to run every ms, and this will work
better when n>1.
-SteveK
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Re: [Asterisk-Dev] High resolution timers using POSIX clocks instead of zaptel
Tilghman Lesher wrote: On Friday 27 May 2005 05:33, David Woodhouse wrote: Using zaptel just for a time source is silly. We should use POSIX timers instead. Here's a start, but I don't know how long it'll be before I can get to finish it, so I thought I'd post it here in the hope that someone else will pick it up. As noted here: http://lists.digium.com/pipermail/asterisk-users/2002-April/002072.html software timers are lacking. Call me slow, or just a user, but I don't understand your response. I can't tell if you're agreeing with David's post, or not. I read the link, it's to a brainstorm about using USB as a timing source. Is that the "software timer" that's lacking, or is it the POSIX implementation you're referring to? /me says "huh?" -- Andrew Thompson http://aktzero.com/ begin:vcard fn:Andrew Thompson n:Thompson;Andrew email;internet:[EMAIL PROTECTED] x-mozilla-html:FALSE url:http://aktzero.com/ version:2.1 end:vcard ___ Asterisk-Dev mailing list Asterisk-Dev@lists.digium.com http://lists.digium.com/mailman/listinfo/asterisk-dev To UNSUBSCRIBE or update options visit: http://lists.digium.com/mailman/listinfo/asterisk-dev
Re: [Asterisk-Dev] High resolution timers using POSIX clocks instead of zaptel
On Friday 27 May 2005 05:33, David Woodhouse wrote: > Using zaptel just for a time source is silly. We should use POSIX > timers instead. Here's a start, but I don't know how long it'll be > before I can get to finish it, so I thought I'd post it here in the > hope that someone else will pick it up. As noted here: http://lists.digium.com/pipermail/asterisk-users/2002-April/002072.html software timers are lacking. -- Tilghman ___ Asterisk-Dev mailing list Asterisk-Dev@lists.digium.com http://lists.digium.com/mailman/listinfo/asterisk-dev To UNSUBSCRIBE or update options visit: http://lists.digium.com/mailman/listinfo/asterisk-dev
