Function prof_sample_threshold_update

deps/jemalloc/src/prof.c:1139–1180

* The bodies of this function and prof_leakcheck() are compiled out unless heap * profiling is enabled, so that it is possible to compile jemalloc with * floating point support completely disabled. Avoiding floating point code is * important on memory-constrained systems, but it also enables a workaround for * versions of glibc that don't properly save/restore floating point registers * duri

 * -mno-sse) in order for the workaround to be complete.
 */
void
prof_sample_threshold_update(prof_tdata_t *tdata) {
#ifdef JEMALLOC_PROF
	if (!config_prof) {
		return;
	}

	if (lg_prof_sample == 0) {
		tsd_bytes_until_sample_set(tsd_fetch(), 0);
		return;
	}

	/*
	 * Compute sample interval as a geometrically distributed random
	 * variable with mean (2^lg_prof_sample).
	 *
	 *                             __        __
	 *                             |  log(u)  |                     1
	 * tdata->bytes_until_sample = | -------- |, where p = ---------------
	 *                             | log(1-p) |             lg_prof_sample
	 *                                                     2
	 *
	 * For more information on the math, see:
	 *
	 *   Non-Uniform Random Variate Generation
	 *   Luc Devroye
	 *   Springer-Verlag, New York, 1986
	 *   pp 500
	 *   (http://luc.devroye.org/rnbookindex.html)
	 */
	uint64_t r = prng_lg_range_u64(&tdata->prng_state, 53);
	double u = (double)r * (1.0/9007199254740992.0L);
	uint64_t bytes_until_sample = (uint64_t)(log(u) /
	    log(1.0 - (1.0 / (double)((uint64_t)1U << lg_prof_sample))))
	    + (uint64_t)1U;
	if (bytes_until_sample > SSIZE_MAX) {
		bytes_until_sample = SSIZE_MAX;
	}
	tsd_bytes_until_sample_set(tsd_fetch(), bytes_until_sample);

#endif
}

#ifdef JEMALLOC_JET
static prof_tdata_t *