Same as now_cpu_time(), but for fast queries (less accurate)
Relies on now_cpu_time() and now_mono_time_fast() is used
as a cache expiration hint to prevent now_cpu_time() from being
called too often since it is known to be quite expensive.
Depends on commit "MINOR: clock: add now_mono_time_fast() function"
Same as now_mono_time(), but for fast queries (less accurate)
Relies on coarse clock source (also known as fast clock source on
some systems).
Fallback to now_mono_time() if coarse source is not supported on the system.
We've had a start date even before the internal monotonic clock existed,
but once the monotonic clock was added, the start date was not updated
to distinguish the wall clock time units and the internal monotonic time
units. The distinction is important because both clocks do not necessarily
progress at the same speed. The very rare occurrences of the wall-clock
date are essentially for human consumption and communication with third
parties (e.g. report the start date in "show info" for monitoring
purposes). However currently this one is also used to measure the distance
to "now" as being the process' uptime. This is actually not correct. It
only works because for now the two dates are initialized at the exact
same instant at boot but could still be wrong if the system's date shows
a big jump backwards during startup for example. In addition the current
situation prevents us from enforcing an abritrary offset at boot to reveal
some heisenbugs.
This patch adds a new "start_time" at boot that is set from "now" and is
used in uptime calculations. "start_date" instead is now set from "date"
and will always reflect the system date for human consumption (e.g. in
"show info"). This way we're now sure that any drift of the internal
clock relative to the system date will not impact the reported uptime.
This could possibly be backported though it's unlikely that anyone has
ever noticed the problem.
Pollers that support busy polling spend a lot of time (and cause
contention) updating the global date when they're looping over themselves
while it serves no purpose: what's needed is only an update on the local
date to know when to stop looping.
This patch splits clock_pudate_date() into a pair of local and global
update functions, so that pollers can be easily improved.
This removes the knowledge of clockid_t from anywhere but clock.c, thus
eliminating a source of includes burden. The unused clock_id field was
removed from thread_info, and the definition setting of clockid_t was
removed from compat.h. The most visible change is that the function
now_cpu_time_thread() now takes the thread number instead of a tinfo
pointer.
The code that deals with timer creation for the WDT was moved to clock.c
and is called with the few relevant arguments. This removes the need for
awareness of clock_id from wdt.c and as such saves us from having to
share it outside. The timer_t is also known only from both ends but not
from the public API so that we don't have to create a fake timer_t
anymore on systems which do not support it (e.g. macos).
This was previously open-coded in run_thread_poll_loop(). Now that
we have clock.c dedicated to such stuff, let's move the code there
so that we don't need to keep such ifdefs nor to depend on the
clock_id.
The entering_poll/leaving_poll/measure_idle functions that were hard
to classify and used to move to various locations have now been placed
into clock.c since it's precisely about time-keeping. The functions
were renamed to clock_*. The samp_time and idle_time values are now
static since there is no reason for them to be read from outside.
There is currently a problem related to time keeping. We're mixing
the functions to perform calculations with the os-dependent code
needed to retrieve and adjust the local time.
This patch extracts from time.{c,h} the parts that are solely dedicated
to time keeping. These are the "now" or "before_poll" variables for
example, as well as the various now_*() functions that make use of
gettimeofday() and clock_gettime() to retrieve the current time.
The "tv_*" functions moved there were also more appropriately renamed
to "clock_*".
Other parts used to compute stolen time are in other files, they will
have to be picked next.
