osmo_time_cc: rate_ctr presence should not affect counting

Make sure that osmo_time_cc counts exactly the same, regardless of a
rate_ctr being present or not. Only skip sending counter increments when
there is no rate counter, do not affect anything else.

In osmo-bsc, we are discussing a patch where an lchan redirects
osmo_time_cc counter increments to different rate counters depending on
its current type. In my comments I am also claiming that osmo_time_cc
works the same regardless of a rate_ctr being present or not. Looking at
the code, this is not actually the case.

Before this patch, when there is no rate_ctr, the reported_sum would
freeze, and as soon as a rate_ctr shows up, all counter increments from
the previous reported_sum would be sent to the newly set rate_ctr.
Instead, we want counter increments to simply be lost while there is no
rate_ctr set. IOW, rate_ctr == NULL should mean >/dev/null.

Related: I1b0670c47cb5e0b7776eda89d1e71545ba0e3347 (osmo-bsc)
Change-Id: I380b28d7ab0a6c8aab6c7e2a64bc73cab14863d2
changes/25/27425/1
Neels Hofmeyr 9 months ago
parent ef872cb7ad
commit b54229d2ec
  1. 7
      src/time_cc.c

@ -120,8 +120,6 @@ static void osmo_time_cc_report(struct osmo_time_cc *tc, uint64_t now)
{
uint64_t delta;
uint64_t n;
if (!tc->cfg.rate_ctr)
return;
/* We report a sum "rounded up", ahead of time. If the granularity period has not yet elapsed after the last
* reporting, do not report again yet. */
if (tc->reported_sum > tc->sum)
@ -139,7 +137,8 @@ static void osmo_time_cc_report(struct osmo_time_cc *tc, uint64_t now)
/* integer sanity, since rate_ctr_add() takes an int argument. */
if (n > INT_MAX)
n = INT_MAX;
rate_ctr_add(tc->cfg.rate_ctr, n);
if (tc->cfg.rate_ctr)
rate_ctr_add(tc->cfg.rate_ctr, n);
/* Store the increments of gran_usec that were counted. */
tc->reported_sum += n * GRAN_USEC(tc);
}
@ -205,7 +204,7 @@ static void osmo_time_cc_schedule_timer(struct osmo_time_cc *tc, uint64_t now)
next_event = OSMO_MIN(next_event, next_forget_time);
}
/* Next rate_ctr increment? */
if (tc->flag_state && tc->cfg.rate_ctr) {
if (tc->flag_state) {
uint64_t next_inc = now + (tc->reported_sum - tc->sum) + ROUND_THRESHOLD_USEC(tc);
next_event = OSMO_MIN(next_event, next_inc);
}

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