PHP-FPM process strace output:
clock_gettime(CLOCK_MONOTONIC, {768618, 940967711}) = 0
clock_gettime(CLOCK_MONOTONIC, {768618, 941079020}) = 0
clock_gettime(CLOCK_MONOTONIC, {768618, 941197020}) = 0
poll([{fd=11, events=POLLIN|POLLPRI}], 1, 1000) = 0 (Timeout)
poll([{fd=11, events=POLLIN|POLLPRI}], 1, 0) = 0 (Timeout)