From owner-freebsd-current Wed Jun 3 23:57:59 1998 Return-Path: Received: (from majordom@localhost) by hub.freebsd.org (8.8.8/8.8.8) id XAA13078 for freebsd-current-outgoing; Wed, 3 Jun 1998 23:57:59 -0700 (PDT) (envelope-from owner-freebsd-current@FreeBSD.ORG) Received: from antipodes.cdrom.com (castles348.castles.com [208.214.167.48]) by hub.freebsd.org (8.8.8/8.8.8) with ESMTP id XAA13073 for ; Wed, 3 Jun 1998 23:57:56 -0700 (PDT) (envelope-from mike@antipodes.cdrom.com) Received: from antipodes.cdrom.com (localhost [127.0.0.1]) by antipodes.cdrom.com (8.8.8/8.8.5) with ESMTP id WAA00712; Wed, 3 Jun 1998 22:53:35 -0700 (PDT) Message-Id: <199806040553.WAA00712@antipodes.cdrom.com> X-Mailer: exmh version 2.0zeta 7/24/97 To: "Richard S. Straka" cc: current@FreeBSD.ORG Subject: Re: strange behavior with signal latencies In-reply-to: Your message of "Wed, 03 Jun 1998 22:56:51 PDT." <35763722.C34EEF4E@home.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Date: Wed, 03 Jun 1998 22:53:35 -0700 From: Mike Smith Sender: owner-freebsd-current@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG > 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