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| author | bde <bde@FreeBSD.org> | 2007-02-27 04:54:33 +0000 |
|---|---|---|
| committer | bde <bde@FreeBSD.org> | 2007-02-27 04:54:33 +0000 |
| commit | 3ee0d09a443f80fc57dc791114562e66b6856c71 (patch) | |
| tree | ff742b8b2e502413667eeed2507cb703f839ea09 /usr.bin/netstat | |
| parent | 05b92097cb751ac3e6ba126eed272f954f9c7210 (diff) | |
| download | FreeBSD-src-3ee0d09a443f80fc57dc791114562e66b6856c71.zip FreeBSD-src-3ee0d09a443f80fc57dc791114562e66b6856c71.tar.gz | |
Use a periodic itimer instead of repeated calls to alarm() in
sidewaysintpr(). This increases the accuracy of the per-interval
counts when they are interpreted as rates. Repeated calls to alarm(n)
give an average interval that is about 2 ticks larger than n and has
a large variance. Periodic itimers normally get the average almost
right but have similarly large variance (due to scheduling delays).
Statistics utilities should use clock_gettime() to determine the
actual interval, but it is still useful to maximize the accuracy of
the interval, especially for cases like netstat -w where counts are
displayed so the program cannot hide the inaccuracy in a rate
conversion.
Diffstat (limited to 'usr.bin/netstat')
| -rw-r--r-- | usr.bin/netstat/if.c | 16 |
1 files changed, 9 insertions, 7 deletions
diff --git a/usr.bin/netstat/if.c b/usr.bin/netstat/if.c index 80f7be0..280e1bf 100644 --- a/usr.bin/netstat/if.c +++ b/usr.bin/netstat/if.c @@ -531,6 +531,7 @@ sidewaysintpr(unsigned interval1, u_long off) struct ifnet ifnet; u_long firstifnet; struct ifnethead ifnethead; + struct itimerval interval_it; struct iftot *iftot, *ip, *ipn, *total, *sum, *interesting; int line; int oldmask, first; @@ -583,7 +584,10 @@ sidewaysintpr(unsigned interval1, u_long off) (void)signal(SIGALRM, catchalarm); signalled = NO; - (void)alarm(interval1); + interval_it.it_interval.tv_sec = interval1; + interval_it.it_interval.tv_usec = 0; + interval_it.it_value = interval_it.it_interval; + setitimer(ITIMER_REAL, &interval_it, NULL); first = 1; banner: printf("%17s %14s %16s", "input", @@ -668,12 +672,10 @@ loop: putchar('\n'); fflush(stdout); oldmask = sigblock(sigmask(SIGALRM)); - if (! signalled) { + while (!signalled) sigpause(0); - } - sigsetmask(oldmask); signalled = NO; - (void)alarm(interval1); + sigsetmask(oldmask); line++; first = 0; if (line == 21) @@ -684,8 +686,8 @@ loop: } /* - * Called if an interval expires before sidewaysintpr has completed a loop. - * Sets a flag to not wait for the alarm. + * Set a flag to indicate that a signal from the periodic itimer has been + * caught. */ static void catchalarm(int signo __unused) |
