High resolution Sleep

[Charles Zhang]

Sleep() function Sleep at lease 1 millisecond, there is a way to make a
thread to sleep less than a millisecond? One way I know of is using
performance counter which is not really sleep ( loop and check again and
again and uses CPU time).

Thanks

Charles Zhang

[Mark Salsbery [MVP]]

Re: High resolution Sleep

Even Sleep() doesn't have true 1 ms resolution.

There's no better timer than the performance counter in Windows AFAIK.

Mark

--
Mark Salsbery
Microsoft MVP - Visual C++


"Charles Zhang" <CharlesZhang@n ewsgroups.nospa mwrote in message
news:OvGYhdHlIH A.5088@TK2MSFTN GP02.phx.gbl...

Sleep() function Sleep at lease 1 millisecond, there is a way to make a
thread to sleep less than a millisecond? One way I know of is using
performance counter which is not really sleep ( loop and check again and
again and uses CPU time).
>
Thanks
>
Charles Zhang

[Jordi Maycas]

Re: High resolution Sleep

and.. what about with time struct?

hh:mm:ss,dd

where 99>=dd>=0

dd are miliseconds...

and thinking a little more, what about cpu cicles?




"Mark Salsbery [MVP]" <MarkSalsbery[MVP]@newsgroup.nosp amescribió en el
mensaje news:75FC7FFB-9A1E-4537-815F-CEC1FD660331@mi crosoft.com...

Even Sleep() doesn't have true 1 ms resolution.
>
There's no better timer than the performance counter in Windows AFAIK.
>
Mark
>
--
Mark Salsbery
Microsoft MVP - Visual C++
>
>
"Charles Zhang" <CharlesZhang@n ewsgroups.nospa mwrote in message
news:OvGYhdHlIH A.5088@TK2MSFTN GP02.phx.gbl...

>Sleep() function Sleep at lease 1 millisecond, there is a way to make a
>thread to sleep less than a millisecond? One way I know of is using
>performance counter which is not really sleep ( loop and check again and
>again and uses CPU time).
>>
>Thanks
>>
>Charles Zhang

>

[RFOG]

Re: High resolution Sleep

You can use "clockres" from Sysinternals (today Microsoft) to see the
minimum resolution in your machine. Mine (Quad core is 15.6 ms).

I think less than 15 ms is impossible, and surely a sleep of 15 ms becomes
in a lot of more time because Windows uses that sleeping to do other tasks,
and if you put a for() loop you will get your CPU time scalated to 100% and
surely with no more precission that sleep.

"Charles Zhang" <CharlesZhang@n ewsgroups.nospa mwrote in message
news:OvGYhdHlIH A.5088@TK2MSFTN GP02.phx.gbl...

Sleep() function Sleep at lease 1 millisecond, there is a way to make a
thread to sleep less than a millisecond? One way I know of is using
performance counter which is not really sleep ( loop and check again and
again and uses CPU time).
>
Thanks
>
Charles Zhang

--
Microsoft Visual C++ MVP
=============== =========
Mi blog sobre programación: http://geeks.ms/blogs/rfog
Momentos Leves: http://momentosleves.blogspot.com/
Libros, ciencia ficción y programación
=============== =============== ==========
Es un hecho que el hombre tiene que controlar la ciencia y chequear
ocasionalmente el avance de la tecnología.
-- Thomas Henry Huxley.

[Jochen Kalmbach [MVP]]

Re: High resolution Sleep

Hi RFOG!

I think less than 15 ms is impossible, and surely a sleep of 15 ms
becomes in a lot of more time because Windows uses that sleeping to do
other tasks, and if you put a for() loop you will get your CPU time
scalated to 100% and surely with no more precission that sleep.

If you use "timeBeginPerio d(1)" you can mostly reduce the time-slice to
2 ms.

Greetings
Jochen

[Willy Denoyette [MVP]]

Re: High resolution Sleep

"Jochen Kalmbach [MVP]" <nospam-Jochen.Kalmbach @holzma.dewrote in message
news:%232K%238H LlIHA.2304@TK2M SFTNGP05.phx.gb l...

Hi RFOG!
>

>I think less than 15 ms is impossible, and surely a sleep of 15 ms
>becomes in a lot of more time because Windows uses that sleeping to do
>other tasks, and if you put a for() loop you will get your CPU time
>scalated to 100% and surely with no more precission that sleep.

>
If you use "timeBeginPerio d(1)" you can mostly reduce the time-slice to 2
ms.
>
Greetings
Jochen

True, but this won't guarantee that your thread will get scheduled right
after 2ms. The scheduler is master of the game here, once you give up your
quantum, you'll have to wait until all other higher priority threads have
run.

Willy.

[Jochen Kalmbach [MVP]]

Re: High resolution Sleep

Hi Willy!

True, but this won't guarantee that your thread will get scheduled right
after 2ms. The scheduler is master of the game here,

Yes...

once you give up
your quantum, you'll have to wait until all other higher priority
threads have run.

No. If a higher prio thread becomes ready to run, your quantum does not
matter. Your thread will be immediately interrupted and the higher prio
thread will run.

Greetings
Jochen

[Jochen Kalmbach [MVP]]

Re: High resolution Sleep

Hi Willy!

No.

I wanted to say: This is only some side of the truth... sorry...

Greetings
Jochen

[Ben Voigt [C++ MVP]]

Re: High resolution Sleep

Charles Zhang wrote:

Sleep() function Sleep at lease 1 millisecond, there is a way to make
a thread to sleep less than a millisecond? One way I know of is using
performance counter which is not really sleep ( loop and check again
and again and uses CPU time).

Waitable Timers allow the wait to be specified very precisely, however the
actual resolution will depend on the system clock interrupt.
timeBeginPeriod can make the clock interrupt faster to a point, I don't know
of any user-mode way to set the interrupt rate above 1kHz.

>
Thanks
>
Charles Zhang

[Willy Denoyette [MVP]]

Re: High resolution Sleep

"Ben Voigt [C++ MVP]" <rbv@nospam.nos pamwrote in message
news:OkgZkdNlIH A.1212@TK2MSFTN GP05.phx.gbl...

Willy Denoyette [MVP] wrote:

>"Jochen Kalmbach [MVP]" <nospam-Jochen.Kalmbach @holzma.dewrote in
>message news:OFgBKaLlIH A.536@TK2MSFTNG P06.phx.gbl...

>>Hi Willy!
>>>
>>>True, but this won't guarantee that your thread will get scheduled
>>>right after 2ms. The scheduler is master of the game here,
>>>
>>Yes...
>>>
>>>once you give up your quantum, you'll have to wait until all other
>>>higher priority threads have run.
>>>
>>No. If a higher prio thread becomes ready to run, your quantum does
>>not matter. Your thread will be immediately interrupted and the
>>higher prio thread will run.
>>>

>>
>Hi Jochen,
>>
>I mean :
>T1 normal priority calls sleep(2) - that is, give up your quantum now!
>T2 normal priority gets scheduled runs for 1msec and enters a wait
>state T3 higher priority gets scheduled and runs for 1 sec.
>T1 as slept ~1 sec

>
This isn't a drawback to calling sleep though, any wait method could be
pre-empted by a higher priority thread.
>

True, and for the same reason you can't use them to "wait" for an "exact"
(especially small) amount of time when running on a Windows OS (even not on
Windows CE). Point is that once your (1) thread enters a wait state, you are
at the "mercy" of the scheduler to (2) wake you up. You are under control of
the first action, but you aren't of the second.
So whether you call Sleep(1) or WaitForSingleOb ject(..., 1), you will wait
for at *least* the RTC timer interval, whatever it's value.

Willy.

[Mark Salsbery [MVP]]

Re: High resolution Sleep


"Jordi Maycas" <jmaycasNOSPAM@ hotmail.comwrot e in message
news:elS5ZnKlIH A.5396@TK2MSFTN GP06.phx.gbl...

and.. what about with time struct?
>
hh:mm:ss,dd
>
where 99>=dd>=0
>
dd are miliseconds...

Yes, many APIs have 1ms units in parameters. Some use 100-nanosecond units.
But the actual accuracy is much less than 1ms.

See Charles Wang's response below...

>
and thinking a little more, what about cpu cicles?

Now you're at the performance counter level :)

Mark

--
Mark Salsbery
Microsoft MVP - Visual C++

>
>
>
>
"Mark Salsbery [MVP]" <MarkSalsbery[MVP]@newsgroup.nosp amescribió en el
mensaje news:75FC7FFB-9A1E-4537-815F-CEC1FD660331@mi crosoft.com...

>Even Sleep() doesn't have true 1 ms resolution.
>>
>There's no better timer than the performance counter in Windows AFAIK.
>>
>Mark
>>
>--
>Mark Salsbery
>Microsoft MVP - Visual C++
>>
>>
>"Charles Zhang" <CharlesZhang@n ewsgroups.nospa mwrote in message
>news:OvGYhdHlI HA.5088@TK2MSFT NGP02.phx.gbl.. .

>>Sleep() function Sleep at lease 1 millisecond, there is a way to make a
>>thread to sleep less than a millisecond? One way I know of is using
>>performance counter which is not really sleep ( loop and check again and
>>again and uses CPU time).
>>>
>>Thanks
>>>
>>Charles Zhang

>>

>
>

[Pavel A.]

Re: High resolution Sleep

You can get Sleep() delay on XP close to the current timer resolution
but measuring the actual sleep time can be difficult.
I've made a simple test based on Sysinternals clockres sample.

The minimal resolution is 1 or 2 ms on most modern systems where the
default is 15.6 ms, and 1 ms on older systems where the default was 10 ms.
AFAIK there still is no good explanation why the newer PCs have default
resolution 10 ms.

Surprising is that value returned by GetSystemTimeAs FileTime or
NtQuerySystemTi me
seems to update only once in system clock tick (15.6 ms in my case),
so when I call GetSystemTimeAs FileTime before and after Sleep(1), I got
_same_ value 7 times out of 8;
and on 8th time the difference jumps to 15 ms :( So the average Sleep()
delay of many samples is close to 1 ms.

Regards,
--PA

[Ben Voigt [C++ MVP]]

Re: High resolution Sleep

Pavel A. wrote:

You can get Sleep() delay on XP close to the current timer resolution
but measuring the actual sleep time can be difficult.

Not difficult, just use QueryPerformanc eCounter.

I've made a simple test based on Sysinternals clockres sample.
>
The minimal resolution is 1 or 2 ms on most modern systems where the
default is 15.6 ms, and 1 ms on older systems where the default was
10 ms. AFAIK there still is no good explanation why the newer PCs
have default resolution 10 ms.
>
Surprising is that value returned by GetSystemTimeAs FileTime or
NtQuerySystemTi me
seems to update only once in system clock tick (15.6 ms in my case),
so when I call GetSystemTimeAs FileTime before and after Sleep(1), I
got _same_ value 7 times out of 8;
and on 8th time the difference jumps to 15 ms :( So the average
Sleep() delay of many samples is close to 1 ms.
>
Regards,
--PA

[Willy Denoyette [MVP]]

Re: High resolution Sleep

"Pavel A." <pavel_a@NOwrit emeNO.comwrote in message
news:OP8c2zQlIH A.5260@TK2MSFTN GP03.phx.gbl...

You can get Sleep() delay on XP close to the current timer resolution
but measuring the actual sleep time can be difficult.
I've made a simple test based on Sysinternals clockres sample.
>
The minimal resolution is 1 or 2 ms on most modern systems where the
default is 15.6 ms, and 1 ms on older systems where the default was 10 ms.
AFAIK there still is no good explanation why the newer PCs have default
resolution 10 ms.
>
Surprising is that value returned by GetSystemTimeAs FileTime or
NtQuerySystemTi me
seems to update only once in system clock tick (15.6 ms in my case),
so when I call GetSystemTimeAs FileTime before and after Sleep(1), I got
_same_ value 7 times out of 8;
and on 8th time the difference jumps to 15 ms :( So the average Sleep()
delay of many samples is close to 1 ms.
>
Regards,
--PA
>
>

Indeed, measuring is the key, but as I said before, you can't Sleep (or
Wait) for a reliable amount of time,
when sleeping (waiting) for < RTC interval, you give up your remaining
quantum, and you may possibly get re-scheduled after this period of time,
that is, after X msec. where X >= the remaining quantum.
For instance when you call Sleep(1) after your thread has run for Y msec,
you will probably sleep for 15.6 - X msec. on current multi-core/SMP
systems.
When you call Sleep(1) after your thread consumed 10 µsec of it's quantum,
this thread will sleep for at least 15.6 msec.
When you call Sleep(1) after your thread has consumed 14 msec you will sleep
for at least 1.6 msec.
That means you cannot reliably sleep with Windows ;-)

Compile and run the following sample , you'll see what I mean.


#ifndef _WIN32_WINNT
#define _WIN32_WINNT 0x0500
#endif
#define WIN32_LEAN_AND_ MEAN
#include <windows.h>
#include <process.h>
#include <cstdio>
#include <math.h>
unsigned __stdcall Run(void* dummy)
{
double r = 0.0;
for(int i = 0; i < 50000000; i++)
{
r += (double)sqrt((d ouble)i);
}
printf_s("%Lf\n ", r);
_endthreadex(0) ;
return 0;
}
int main() {
__int64 startcount, stopCount, frequ;
QueryPerformanc eFrequency((LAR GE_INTEGER*)&fr equ);
HANDLE tHandle;
unsigned thread_Id;
Sleep(1); // Give up the current quantum so we can start with a fresh one
after return
tHandle = reinterpret_cas t<HANDLE>(_begi nthreadex(0, 0, &Run, 0, 0,
&thread_Id ));
QueryPerformanc eCounter((LARGE _INTEGER*)&star tcount);
Sleep(1);
//Or, use next
// WaitForSingleOb ject(tHandle, 1); // wait for thread to finish or timeout
QueryPerformanc eCounter((LARGE _INTEGER*)&stop Count);
CloseHandle(tHa ndle);
printf_s("%Lf seconds\n", (double)(stopCo unt - startcount)/frequ);
return 0;
}



Willy.