Messages in this thread | | | From | "David Engraf" <> | Subject | Re: [PATCH] Win32 equivalent to GetTickCount systemcall (i386) | Date | Tue, 6 Dec 2005 12:23:23 +0100 |
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> On Tue, 2005-12-06 at 11:36 +0100, David Engraf wrote: > > This patch adds a new systemcall on i386 architectures returning the jiffies > > value to the application. > > As a kernel developer you can use jiffies but from the user space there is > > no equivalent function which counts every millisecond like the Win32 > > GetTickCount.
> a few comments
> 1) jiffies are 64 bit not 32
Jiffies is defined as "unsigned long volatile __jiffy_data jiffies". On i386 machines unsigned long is 32.
> 2) jiffies are not a constant time, eg HZ is a config option, > exposing that internal counter to userspace sounds wrong, after > all what would it be used for
Right, HZ is defined as USER_HZ which can be set over the config. On normal desktop systems it should be 1000 on other machines it could also be 100 or 250. Either we can ignore the setting and the function depends on the USER_HZ config, or we have to calculate the right value with USER_HZ.
> 3) wouldn't it be better to expose a wallclock time thing which > has a constant unit of time between all kernels?
What is it?
> (and.. wait.. isn't that called gettimeofday() ) Not really gettimeofday is based on the date and time, but what if the user changes the date, the counter would also change.
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