frequency, quality and current value of each available time counter.
At the moment all of these are read-only, but it might make sense to
make some of these read-write in the future.
MFC after: 3 months
Keep accounting time (in per-cpu) cputicks and the statistics counts
in the thread and summarize into struct proc when at context switch.
Don't reach across CPUs in calcru().
Add code to calibrate the top speed of cpu_tickrate() for variable
cpu_tick hardware (like TSC on power managed machines).
Don't enforce monotonicity (at least for now) in calcru. While the
calibrated cpu_tickrate ramps up it may not be true.
Use 27MHz counter on i386/Geode.
Use TSC on amd64 & i386 if present.
Use tick counter on sparc64
Keep track of time spent by the cpu in various contexts in units of
"cputicks" and scale to real-world microsec^H^H^H^H^H^H^H^Hclock_t
only when somebody wants to inspect the numbers.
For now "cputicks" are still derived from the current timecounter
and therefore things should by definition remain sensible also on
SMP machines. (The main reason for this first milestone commit is
to verify that hypothesis.)
On slower machines, the avoided multiplications to normalize timestams
at every context switch, comes out as a 5-7% better score on the
unixbench/context1 microbenchmark. On more modern hardware no change
in performance is seen.
sysctl routines and state. Add some code to use it for signalling the need
to downconvert a data structure to 32 bits on a 64 bit OS when requested by
a 32 bit app.
I tried to do this in a generic abi wrapper that intercepted the sysctl
oid's, or looked up the format string etc, but it was a real can of worms
that turned into a fragile mess before I even got it partially working.
With this, we can now run 'sysctl -a' on a 32 bit sysctl binary and have
it not abort. Things like netstat, ps, etc have a long way to go.
This also fixes a bug in the kern.ps_strings and kern.usrstack hacks.
These do matter very much because they are used by libc_r and other things.
Give the HZ/overflow check a 10% margin.
Eliminate bogus newline.
If timecounters have equal quality, prefer higher frequency.
Some inspiration from: bde
represents the pruely stylistic changes and should have no net impact
on the rest of the code.
bde's more substantive changes will follow in a separate commit once
we've come to closure on them.
Submitted by: bde
ntp_update_second twice when we have a large step in case that step
goes across a scheduled leap second. The only way this could happen
would be if we didn't call tc_windup over the end of day on the day of
a leap second, which would only happen if timeouts were delayed for
seconds. While it is an edge case, it is an important one to get
right for my employer.
Sponsored by: Timing Solutions Corporation
A timecounter will be selected when registered if its quality is
not negative and no less than the current timecounters.
Add a sysctl to report all available timecounters and their qualities.
Give the dummy timecounter a solid negative quality of minus a million.
Give the i8254 zero and the ACPI 1000.
The TSC gets 800, unless APM or SMP forces it negative.
Other timecounters default to zero quality and thereby retain current
selection behaviour.
Before, we would add/subtract the leap second when the system had been
up for an even multiple of days, rather than at the end of the day, as
a leap second is defined (at least wrt ntp). We do this by
calculating the notion of UTC earlier in the loop, and passing that to
get it adjusted. Any adjustments that ntp_update_second makes to this
time are then transferred to boot time. We can't pass it either the
boot time or the uptime because their sum is what determines when a
leap second is needed. This code adds an extra assignment and two
extra compare in the typical case, which is as cheap as I could made
it.
I have confirmed with this code the kernel time does the correct thing
for both positive and negative leap seconds. Since the ntp interface
doesn't allow for +2 or -2, those cases can't be tested (and the folks
in the know here say there will never be a +2s or -2s leap event, but
rather two +1s or -1s leap events).
There will very likely be no leap seconds for a while, given how the
earth is speeding up and slowing down, so there will be plenty of time
for this fix to propigate. UT1-UTC is currently at "about -0.4s" and
decrementing by .1s every 8 months or so. 6 * 8 is 48 months, or 4
years.
-stable has different code, but a similar bug that was introduced
about the time of the last leap second, which is why nobody has
noticed until now.
MFC After: 3 weeks
Reviewed by: phk
"Furthermore, leap seconds must die." -- Cato the Elder
potential discontinuities in our UTC timescale.
Applications can monitor this variable if they want to be informed
about steps in the timescale. Slews (ntp and adjtime(2)) and
frequency adjustments (ntp) will not increment this counter, only
operations which set the clock. No attempt is made to classify
size or direction of the step.
called. Otherwise (depending on a non-deterministic sort), the timecounter
code can be initialized before the clock rate has been set (on ia64) and it
assumes hz = 100, rather than the real value of 1024. I'm not sure how much
gets upset by this.
Glanced at by: phk
functions which run for several milliseconds at a time and getting
in queue behind one or more of those makes us miss our rewind.
Instead call it from hardclock() like we used to do, but retain the
prescaler so we still cope with high HZ values.
