Jesper Juhl schreef:
On 21/01/2008, Christian Boon <chris.boon@xxxxxxxxx> wrote:
Jesper Juhl schreef:
On 21/01/2008, Christian Boon <chris.boon@xxxxxxxxx> wrote:
Hello,
For my ARM processor (PXA255) i use kernel 2.6.22 and a kernel HZ value
of 1000.
[snip]
Am i doing something wrong here? Is this value converted to some sort of
userspace HZ?
I have tried it on x86 also and it gives the same behaviour.
In old kernels the HZ value (in both kernel- and user-space) was 100
without the ability to change this.
When the kernel added the option of other HZ values this was
implemented as kernel-space only and the HZ value exposed to
user-space was fixed at 100. This was done to avoid breaking
applications that assumed a fixed HZ of 100.
So, while the kernel may tick at 100, 250, 1000 or some other HZ
values (or even be tick less), user-space will always see HZ as being
100.
Ok thanks,
is there another way to receive the tick counter in userspace?
I don't know of one, but that doesn't mean there isn't any :)
But, why does your application care?
If it needs to sleep for some amount of time it should just do so with
sleep(), usleep(), select() or similar - it shouldn't need to know
what the kernel Hz is...
If it needs to know the amount of wall-clock time that has passed,
then calling gettimeofday(), at intervals, is usually good enough.
I'm currious as to why you need this...?
In my application i use a shared memory segment with multiple clients
connected.
I wanted to use the tick value as change counter.
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