Date: Wed, 03 Jun 1998 22:53:35 -0700 From: Mike Smith <mike@smith.net.au> To: "Richard S. Straka" <straka@home.com> Cc: current@FreeBSD.ORG Subject: Re: strange behavior with signal latencies Message-ID: <199806040553.WAA00712@antipodes.cdrom.com> In-Reply-To: Your message of "Wed, 03 Jun 1998 22:56:51 PDT." <35763722.C34EEF4E@home.com>
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> I wrote a small test program to look at latencies of user space > processes waking up on the delivery of signals. The program (which is > included in this e-mail) sigsuspend's waiting for a SIGALARM which is > being delivered at 10ms. Upon receipt of the signal, the process wakes > up and records time from the receipt of the last signal using > gettimeofday, then suspends waiting for the next signal. This test was > run on both my P133 running current which was cvsuped on 30 May, and > also my 486-100 running 2.2.6R. Both machines were otherwise completely > idle and the program was run using rtprio 16. > > In looking at the results, I noticed that that the current box exhibited > a 2300 microsecond additional delay every 10th signal or at 100ms > intervals. Also, occationally a signal is missed. I have also noticed > recently using top and systat that current has been consuming between > 1.6% and 3.1% of my P133 in interrupt handling. This seems to > correspond to the latancy I am seeing with the signal test code. I > changed the quantum interval using sysctl to 20 ticks. This had no > effect, the 2300 microsecond latency still appeared at 10Hz. > > The results with 2.2.6R on the 486-100 box showed no signs of the > latency and appeared to always reliably wakeup on every signal. Also, > when the machine is completely idle, the interrupt load is 0.0%, > occationally jumping to 0.4% when the disks sync. > > What in the system is generating the additional processor load at 10Hz > and why am I occationally missing signals? I can't answer the second, but I suspect that you have a different set of drivers active between the two systems, and one of those active on the -current system is scheduling a watchdog routine at hz/10. -- \\ Sometimes you're ahead, \\ Mike Smith \\ sometimes you're behind. \\ mike@smith.net.au \\ The race is long, and in the \\ msmith@freebsd.org \\ end it's only with yourself. \\ msmith@cdrom.com To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-current" in the body of the message
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