Re: [PATCH] Win32 equivalent to GetTickCount systemcall (i386)

Arjan van de Ven
2005-12-06T11:35:20Z

On Tue, 2005-12-06 at 12:23 +0100, David Engraf wrote:
> > 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.

but it's a subvariable of jiffies64 which is 64 bit
>
>
> > 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.

but then.. why?