How to read the processor number?
JF Larvoire
I need to read the current processor number in a WIN32 program.
How can this be done?
Better still, is there a way to do it WITHOUT having to write an ad-hoc
device driver?
Thanks for any clue,
Jean-François
PS. The reason I need to know this number is because I'm reading the CPU
Time Stamp Counter register for measuring very short durations.
On my system (a bi-processor) it happens that both processors have almost
the same counts at the same time. But I'm not sure it's guarantied to be the
case in general.
Brad Staff
news:3e3fe4fb$0$235$626a...@news.free.fr...
You can force your process to run on a particular processor using the Win32
API SetProcessAffinityMask().
Regards,
Brad
Maxim S. Shatskih
CPU
> Time Stamp Counter register for measuring very short durations.
> On my system (a bi-processor) it happens that both processors have
almost
> the same counts at the same time. But I'm not sure it's guarantied
to be the
> case in general.
This is not guaranteed, use the affinity mask to bind the thread to a
particular CPU to guarantee this.
Max
JF Larvoire
The problem is that there's no corresponding GetProcessAffinityMask()
But even if there were, what I actually need is a GetCurrentProcessor()!
JF
Leo Havmøller
> I know about SetProcessAffinityMask().
> The problem is that there's no corresponding GetProcessAffinityMask()
Yes there is!
http://msdn.microsoft.com/library/default.asp?url=/library/en-us/dllproc/bas
e/getprocessaffinitymask.asp
> But even if there were, what I actually need is a GetCurrentProcessor()!
There is not GetCurrentProcessor, because that is not relevant for user-mode
apps. They cannot run at elevated IRQL.
Leo Havmøller.
EMP
If you're running on a Pentium4 you can do CPUID (with eax = 1) and look at
the Local APIC ID in bits 31:24 of returned ebx. That will be unique for each
processor.
Don't know how to do it from user-mode on P5/P6 type processors.
Enio.
Brad Staff
> The problem is that there's no corresponding GetProcessAffinityMask()
http://msdn.microsoft.com/library/default.asp?url=/library/en-us/dllproc/bas
e/getprocessaffinitymask.asp
> But even if there were, what I actually need is a GetCurrentProcessor()!
http://msdn.microsoft.com/library/default.asp?url=/library/en-us/dllproc/bas
e/multiple_processors.asp?frame=true.
The section on Thread Scheduling in "Inside Microsoft Windows 2000" (Solomon
and Russinovich) provides additional information.
Regards,
Brad
Don Burn
"JF Larvoire" <jean-francois.larvoire@remove_this.free.fr> wrote in message
news:3e3fe4fb$0$235$626a...@news.free.fr...
internal
calls and tracking. As long as you can handle a few counts difference don't
worry about the cpu.
Don Burn
Egenera, Inc
EMP
>
> If you're running on a Pentium4 you can do CPUID (with eax = 1) and look at
> the Local APIC ID in bits 31:24 of returned ebx. That will be unique for each
> processor.
> Don't know how to do it from user-mode on P5/P6 type processors.
>
that the CPUID and the RDTSC will be executed on the same processor.
The thread can be time-sliced out between instructions or an interrupt
can occur and the thread can be re-dispatched on another processor.