Re: [PATCH v2] timekeeping: get_jiffies_boot_64() for jiffies that include sleep time
From: Arnd Bergmann
Date: Wed Jun 19 2019 - 17:02:42 EST
On Wed, Jun 19, 2019 at 10:07 PM Jason A. Donenfeld <Jason@xxxxxxxxx> wrote:
> On Wed, Jun 19, 2019 at 10:02 PM Arnd Bergmann <arnd@xxxxxxxx> wrote:
> > > get_jiffies_boot_64 26
> > > ktime_get_coarse_boottime 26
> > > ktime_get_boot_fast_ns with tsc 70
> > > ktime_get_boot_fast_ns with hpet 4922
> > > ktime_get_boot_fast_ns with acpi_pm 1884
> > >
> > > As expected, hpet is really quite painful.
> > I would prefer not to add the new interface then. We might in
> > fact move users of get_jiffies_64() to ktime_get_coarse() for
> > consistency given the small overhead of that function.
> In light of the measurements, that seems like a good plan to me.
> One thing to consider with moving jiffies users over that way is
> ktime_t. Do you want to introduce helpers like
> ktime_get_boot_coarse_ns(), just like there is already with the other
> various functions like ktime_get_boot_ns(), ktime_get_boot_fast_ns(),
> etc? (I'd personally prefer using the _ns variants, at least.) I can
> send a patch for this.
That sounds reasonable, but then I think we should have the full
set of coarse_*_ns() functions, again for consistency:
and document them in Documentation/core-api/timekeeping.rst.
We seem to also be lacking the basic ktime_get_coarse(), which
seems like a major omission.
Both ktime_get_coarse_ns and ktime_get_coarse can be wrappers
around ktime_get_coarse_ts64() then, while the others would