Re: [RFC PATCH Mach] Add a mach host operation which returns elapsed time since bootup

[Zhaoming Luo]

On 12/19/24 4:18 AM, Luca wrote:
> Hi,
Hello,
> Il 18/12/24 02:20, Zhaoming Luo ha scritto:
> > The precision of this implmentation is 10ms. Not sure how to do with the
> > possible data race.
> >
> > Signed-off-by: Zhaoming Luo <zhmingluo@163.com>
> > ---
> >   include/mach/mach_host.defs |  7 +++++++
> >   kern/mach_clock.c           | 20 ++++++++++++++++++++
> >   2 files changed, 27 insertions(+)
> >
> > diff --git a/include/mach/mach_host.defs b/include/mach/mach_host.defs
> > index 8fd9d6b3..67f72cda 100644
> > --- a/include/mach/mach_host.defs
> > +++ b/include/mach/mach_host.defs
> > @@ -386,3 +386,10 @@ routine    host_adjust_time64(
> >   routine    host_get_kernel_version(
> >           host        : host_t;
> >       out    kernel_version    : new_kernel_version_t);
> > +
> > +/*
> > + *    Get the elapsed time on this host.
> > + */
> > +routine    host_get_elapsed_time(
> > +        host        : host_t;
> > +    out    elapsed_time    : time_value_t);
>
> Why not expose this with a kernel device that can be memory mapped, as 
> done by the "time" device?
To be honest I came across /dev/time several times but I'm still quite 
confused about it. I tried to read the documentation and the code of 
storeio translator (`showtrans /dev/time` gave me /hurd/storeio ...) but 
I didn't find something useful. May I have a detail explanation about 
the "time" device? (purpose and mechanism). Or any documentation that's 
worth to read?

Best,
--
Zhaoming Luo