getting the number of cores in kernel

NTDEV
1

Here is a simple one that just keeps me confused.

If I want to get the number of cores in a CPU, I can write this
code(which works fine in user mode):

SYSTEM_INFO sysinfo;

GetSystemInfo( &sysinfo );

n_cores = sysinfo.dwNumberOfProcessors;

For some reason, this code does not compile for kernel and seems to want
winbase.h which then messes up the rest of my code.

Any ideas ?

2

xxxxx@emc.com wrote:

Here is a simple one that just keeps me confused.

If I want to get the number of cores in a CPU, I can write this
code(which works fine in user mode):

SYSTEM_INFO sysinfo;

GetSystemInfo( &sysinfo );

n_cores = sysinfo.dwNumberOfProcessors;

For some reason, this code does not compile for kernel and seems to
want winbase.h which then messes up the rest of my code.

Of course. That’s a user-mode API. User mode and kernel mode have
entirely different APIs. However, 60 seconds with Google should have
brought you to the answer

The kernel exports a variable called KeNumberProcessors that provides
this value, although it’s no longer a “blessed” solution in Windows
Server 2008 and beyond, because processors can come and go.
KeQueryActiveProcessors returns a bitmask showing which processors are
active.

–
Tim Roberts, xxxxx@probo.com
Providenza & Boekelheide, Inc.

3

And KeQueryActiveProcessorCount returns a count so you don’t have to
count the bits yourself.

Mark Roddy

On Mon, Nov 8, 2010 at 3:09 PM, Tim Roberts wrote:
> xxxxx@emc.com wrote:
>>
>> Here is a simple one that just keeps me confused.
>>
>> If I want to get the number of cores in a CPU, I can write this
>> code(which works fine in user mode):
>>
>>
>>
>> SYSTEM_INFO sysinfo;
>>
>> GetSystemInfo( &sysinfo );
>>
>> n_cores = sysinfo.dwNumberOfProcessors;
>>
>>
>>
>> For some reason, this code does not compile for kernel and seems to
>> want winbase.h which then messes up the rest of my code.
>>
>
> Of course. ?That’s a user-mode API. ?User mode and kernel mode have
> entirely different APIs. ?However, 60 seconds with Google should have
> brought you to the answer
>
> The kernel exports a variable called KeNumberProcessors that provides
> this value, although it’s no longer a “blessed” solution in Windows
> Server 2008 and beyond, because processors can come and go.
> KeQueryActiveProcessors returns a bitmask showing which processors are
> active.
>
> –
> Tim Roberts, xxxxx@probo.com
> Providenza & Boekelheide, Inc.
>
>
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