[PATCH v3 libinput] util: introduce ratelimit helpers
Peter Hutterer
peter.hutterer at who-t.net
Thu Nov 6 15:37:23 PST 2014
On Thu, Nov 06, 2014 at 11:46:30PM +0100, David Herrmann wrote:
> Hi
>
> On Thu, Nov 6, 2014 at 11:39 PM, Peter Hutterer
> <peter.hutterer at who-t.net> wrote:
> > From: David Herrmann <dh.herrmann at gmail.com>
> >
> > This adds "struct ratelimit" and "ratelimit_test()". It's a very simple
> > rate-limit helper modeled after Linux' lib/ratelimit.c by Dave Young.
> >
> > This comes in handy to limit log-messages in possible busy loops etc..
> >
> > Signed-off-by: David Herrmann <dh.herrmann at gmail.com>
> > Reviewed-by: Peter Hutterer <peter.hutterer at who-t.net>
> > Signed-off-by: Peter Hutterer <peter.hutterer at who-t.net>
> > ---
> > The test succeeded but not in valgrind which slows everything down enough
> > that we didn't trigger the rate limit (valgrind is part of make check). I
> > though of adding extra flags to detect when we're running valgrind but it's
> > simpler to just extend the timeouts a bit.
> > So instead of 10 msg per 10ms it's 10 per 100ms, the wait is 20ms and then
> > another 90ms to go definitely above the 100ms.
> > And only loop three times, otherwise we trigger the generic test timeout
> > detection.
> >
> > Changes to v3:
> > - ck_assert(a == b) -> ck_assert_int_eq(a, b)
> > - timeouts tweaked to avoid test failures when running through valgrind
>
> Wow, I'm no longer the one with the slowest laptop! ;)
>
> Btw., the ck_assert_*() helpers are the bottleneck, not valgrind (at
> least that's my guess based on previous performance-problems with
> ck_assert).
fwiw, I had the problem of the test consistently succeeding normally but
failing under valgrind. so it was definitely valgrind's influence here.
> So we could maybe also try something like:
>
> if (!$condition)
> ck_assert($condition);
>
> That fixed my code last time, but totally untested and maybe libcheck
> does that automatically now. Your patch is fine, too. No objections
> from my side.
that'd be something I'd rather change/fix in libcheck, not work around in
our tests. Quick skim of libcheck shows that it's translating any
ck_assert into function call to _ck_assert_msg() which logs the position and
then does nothing if the condition is met. Not much to optimise there
though, so I'll stick with the extended timeouts for now.
Cheers,
Peter
> > src/libinput-util.c | 48 ++++++++++++++++++++++++++++++++++++++++++++++++
> > src/libinput-util.h | 16 ++++++++++++++++
> > test/misc.c | 42 ++++++++++++++++++++++++++++++++++++++++++
> > 3 files changed, 106 insertions(+)
> >
> > diff --git a/src/libinput-util.c b/src/libinput-util.c
> > index eeb9786..34d5549 100644
> > --- a/src/libinput-util.c
> > +++ b/src/libinput-util.c
> > @@ -65,3 +65,51 @@ list_empty(const struct list *list)
> > {
> > return list->next == list;
> > }
> > +
> > +void
> > +ratelimit_init(struct ratelimit *r, uint64_t ival_ms, unsigned int burst)
> > +{
> > + r->interval = ival_ms;
> > + r->begin = 0;
> > + r->burst = burst;
> > + r->num = 0;
> > +}
> > +
> > +/*
> > + * Perform rate-limit test. Returns RATELIMIT_PASS if the rate-limited action
> > + * is still allowed, RATELIMIT_THRESHOLD if the limit has been reached with
> > + * this call, and RATELIMIT_EXCEEDED if you're beyond the threshold.
> > + * It's safe to treat the return-value as boolean, if you're not interested in
> > + * the exact state. It evaluates to "true" if the threshold hasn't been
> > + * exceeded, yet.
> > + *
> > + * The ratelimit object must be initialized via ratelimit_init().
> > + *
> > + * Modelled after Linux' lib/ratelimit.c by Dave Young
> > + * <hidave.darkstar at gmail.com>, which is licensed GPLv2.
> > + */
> > +enum ratelimit_state
> > +ratelimit_test(struct ratelimit *r)
> > +{
> > + struct timespec ts;
> > + uint64_t mtime;
> > +
> > + if (r->interval <= 0 || r->burst <= 0)
> > + return RATELIMIT_PASS;
> > +
> > + clock_gettime(CLOCK_MONOTONIC, &ts);
> > + mtime = ts.tv_sec * 1000 + ts.tv_nsec / 1000 / 1000;
> > +
> > + if (r->begin <= 0 || r->begin + r->interval < mtime) {
> > + /* reset counter */
> > + r->begin = mtime;
> > + r->num = 1;
> > + return RATELIMIT_PASS;
> > + } else if (r->num < r->burst) {
> > + /* continue burst */
> > + return (++r->num == r->burst) ? RATELIMIT_THRESHOLD
> > + : RATELIMIT_PASS;
> > + }
> > +
> > + return RATELIMIT_EXCEEDED;
> > +}
> > diff --git a/src/libinput-util.h b/src/libinput-util.h
> > index 51759e8..909c9db 100644
> > --- a/src/libinput-util.h
> > +++ b/src/libinput-util.h
> > @@ -280,4 +280,20 @@ matrix_to_farray6(const struct matrix *m, float out[6])
> > out[5] = m->val[1][2];
> > }
> >
> > +enum ratelimit_state {
> > + RATELIMIT_EXCEEDED,
> > + RATELIMIT_THRESHOLD,
> > + RATELIMIT_PASS,
> > +};
> > +
> > +struct ratelimit {
> > + uint64_t interval;
> > + uint64_t begin;
> > + unsigned int burst;
> > + unsigned int num;
> > +};
> > +
> > +void ratelimit_init(struct ratelimit *r, uint64_t ival_ms, unsigned int burst);
> > +enum ratelimit_state ratelimit_test(struct ratelimit *r);
> > +
> > #endif /* LIBINPUT_UTIL_H */
> > diff --git a/test/misc.c b/test/misc.c
> > index 1512180..38320f3 100644
> > --- a/test/misc.c
> > +++ b/test/misc.c
> > @@ -508,6 +508,46 @@ START_TEST(matrix_helpers)
> > }
> > END_TEST
> >
> > +START_TEST(ratelimit_helpers)
> > +{
> > + struct ratelimit rl;
> > + unsigned int i, j;
> > +
> > + /* 10 attempts every 100ms */
> > + ratelimit_init(&rl, 100, 10);
> > +
> > + for (j = 0; j < 3; ++j) {
> > + /* a burst of 9 attempts must succeed */
> > + for (i = 0; i < 9; ++i) {
> > + ck_assert_int_eq(ratelimit_test(&rl),
> > + RATELIMIT_PASS);
> > + }
> > +
> > + /* the 10th attempt reaches the threshold */
> > + ck_assert_int_eq(ratelimit_test(&rl), RATELIMIT_THRESHOLD);
> > +
> > + /* ..then further attempts must fail.. */
> > + ck_assert_int_eq(ratelimit_test(&rl), RATELIMIT_EXCEEDED);
> > +
> > + /* ..regardless of how often we try. */
> > + for (i = 0; i < 100; ++i) {
> > + ck_assert_int_eq(ratelimit_test(&rl),
> > + RATELIMIT_EXCEEDED);
> > + }
> > +
> > + /* ..even after waiting 20ms */
> > + msleep(20);
> > + for (i = 0; i < 100; ++i) {
> > + ck_assert_int_eq(ratelimit_test(&rl),
> > + RATELIMIT_EXCEEDED);
> > + }
> > +
> > + /* but after 100ms the counter is reset */
> > + msleep(90); /* +10ms to account for time drifts */
> > + }
> > +}
> > +END_TEST
> > +
> > int main (int argc, char **argv) {
> > litest_add_no_device("events:conversion", event_conversion_device_notify);
> > litest_add_no_device("events:conversion", event_conversion_pointer);
> > @@ -519,5 +559,7 @@ int main (int argc, char **argv) {
> > litest_add_no_device("config:status string", config_status_string);
> >
> > litest_add_no_device("misc:matrix", matrix_helpers);
> > + litest_add_no_device("misc:ratelimit", ratelimit_helpers);
> > +
> > return litest_run(argc, argv);
> > }
> > --
> > 2.1.0
> >
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