From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Fri, 14 Mar 2003 03:19:45 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Fri, 14 Mar 2003 03:19:45 -0500 Received: from proxy.povodiodry.cz ([62.77.115.11]:29334 "HELO pc11.op.pod.cz") by vger.kernel.org with SMTP id ; Fri, 14 Mar 2003 03:19:42 -0500 From: "Vitezslav Samel" Date: Fri, 14 Mar 2003 09:30:27 +0100 To: linux-kernel@vger.kernel.org Subject: [BUG] nanosleep() granularity bumps up in 2.5.64 Message-ID: <20030314083027.GA28082@pc11.op.pod.cz> Mail-Followup-To: linux-kernel@vger.kernel.org Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.4i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Hi! When playing with select() timeout values I found that granularity of nanosleep() in 2.5.64 kernel bumps to 256 msec. Trying to get finer granularity it ends up sleeping to the next multiple of 256 msec (only for values > 256 msec): see this (for three last kernels) (measured with attached program): 2.5.62 2.5.63 2.5.64 ------ ------ ------ nanosleep(0.000): delay = 0.000 s 0.001 s 0.000 s nanosleep(0.050): delay = 0.050 s 0.049 s 0.049 s nanosleep(0.100): delay = 0.100 s 0.099 s 0.099 s nanosleep(0.150): delay = 0.150 s 0.149 s 0.149 s nanosleep(0.200): delay = 0.200 s 0.199 s 0.199 s nanosleep(0.250): delay = 0.250 s 0.249 s 0.249 s nanosleep(0.300): delay = 0.300 s 0.299 s 0.511 s nanosleep(0.350): delay = 0.350 s 0.349 s 0.512 s nanosleep(0.400): delay = 0.400 s 0.399 s 0.511 s nanosleep(0.450): delay = 0.450 s 0.449 s 0.512 s nanosleep(0.500): delay = 0.500 s 0.499 s 0.511 s nanosleep(0.550): delay = 0.550 s 0.549 s 0.767 s nanosleep(0.600): delay = 0.600 s 0.599 s 0.767 s nanosleep(0.650): delay = 0.650 s 0.649 s 0.767 s nanosleep(0.700): delay = 0.700 s 0.699 s 0.767 s nanosleep(0.750): delay = 0.750 s 0.749 s 0.767 s nanosleep(0.800): delay = 0.800 s 0.799 s 1.023 s nanosleep(0.850): delay = 0.850 s 0.849 s 1.023 s nanosleep(0.900): delay = 0.900 s 0.899 s 1.023 s nanosleep(0.950): delay = 0.950 s 0.949 s 1.023 s nanosleep(1.000): delay = 1.000 s 0.999 s 1.023 s nanosleep(1.050): delay = 1.050 s 1.049 s 1.279 s nanosleep(1.100): delay = 1.100 s 1.099 s 1.279 s nanosleep(1.150): delay = 1.150 s 1.149 s 1.279 s nanosleep(1.200): delay = 1.200 s 1.199 s 1.279 s nanosleep(1.250): delay = 1.250 s 1.249 s 1.279 s nanosleep(1.300): delay = 1.300 s 1.299 s 1.535 s nanosleep(1.350): delay = 1.350 s 1.349 s 1.535 s nanosleep(1.400): delay = 1.400 s 1.399 s 1.535 s nanosleep(1.450): delay = 1.450 s 1.449 s 1.535 s nanosleep(1.500): delay = 1.500 s 1.499 s 1.535 s nanosleep(1.550): delay = 1.550 s 1.549 s 1.791 s nanosleep(1.600): delay = 1.600 s 1.599 s 1.791 s nanosleep(1.650): delay = 1.650 s 1.649 s 1.791 s nanosleep(1.700): delay = 1.700 s 1.699 s 1.791 s nanosleep(1.750): delay = 1.750 s 1.749 s 1.791 s nanosleep(1.800): delay = 1.800 s 1.799 s 2.047 s nanosleep(1.850): delay = 1.850 s 1.849 s 2.047 s nanosleep(1.900): delay = 1.900 s 1.899 s 2.047 s nanosleep(1.950): delay = 1.950 s 1.949 s 2.047 s nanosleep(2.000): delay = 2.000 s 1.999 s 2.047 s .... and so on. In 2.5.63 there is a conversion to POSIX timers, but that change is O.K. In the 2.5.64 changelog I didn't found any eye-hitting change. Cheers, Vita ------------------------------------------------------------------ #include #include #include #include int main (void) { struct timespec req, rem; struct timeval old, new; long tim; long delay; int i; gettimeofday(&old, NULL); for (delay = 0; delay <= 2000000000L; delay += 50000000L) { rem.tv_sec = 0; rem.tv_nsec = 0; req.tv_sec = delay / 1000000000L; req.tv_nsec = delay % 1000000000L; for (i = 0; i < 2; i++) { /* get only the second measured value */ int ret; gettimeofday(&old, NULL); ret = nanosleep(&req, &rem); gettimeofday(&new, NULL); tim = (new.tv_sec * 1000000 + new.tv_usec) - (old.tv_sec * 1000000 + old.tv_usec); if (ret == -1) { if (errno == EINTR) { printf("EINTR\n"); i--; } else { perror("nanosleep()"); exit(1); } } } printf("nanosleep(%ld.%03ld): delay = %ld.%03ld s\n", req.tv_sec, req.tv_nsec / 1000000, tim / 1000000, (tim % 1000000) / 1000); fflush(stdout); } return 0; }