From owner-freebsd-hackers Fri Jul 31 14:00:25 1998 Return-Path: Received: (from majordom@localhost) by hub.freebsd.org (8.8.8/8.8.8) id OAA25867 for freebsd-hackers-outgoing; Fri, 31 Jul 1998 14:00:25 -0700 (PDT) (envelope-from owner-freebsd-hackers@FreeBSD.ORG) Received: from bangkok.office.cdsnet.net (bangkok.office.cdsnet.net [204.118.245.23]) by hub.freebsd.org (8.8.8/8.8.8) with ESMTP id OAA25758 for ; Fri, 31 Jul 1998 14:00:08 -0700 (PDT) (envelope-from cts@bangkok.office.cdsnet.net) Received: (from cts@localhost) by bangkok.office.cdsnet.net (8.8.8/8.8.5) id NAA18156; Fri, 31 Jul 1998 13:59:56 -0700 (PDT) Date: Fri, 31 Jul 1998 13:59:56 -0700 (PDT) Message-Id: <199807312059.NAA18156@bangkok.office.cdsnet.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit From: Craig Spannring To: chanders@timing.com (Craig Anderson) Cc: freebsd-hackers@FreeBSD.ORG Subject: Re: Using FreeBSD for data acquisition? (long) In-Reply-To: <199807311853.MAA04187@count.timing.com> References: <199807311853.MAA04187@count.timing.com> X-Mailer: VM 6.31 under Emacs 20.2.1 Sender: owner-freebsd-hackers@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG That pretty much matches what I'm seeing for a server I'm writing. My server must respond in less than 3 seconds. Normally it is able to respond in a millisecond or two, but occasionally it takes around 1000 milliseconds. I've duplicated the problem occurring even under real time priority with no other processes on the machine except for init, pagedaemon, vmdaemon, update, and one csh. I had virtual memory disabled to eliminate any paging activity. I tracked the problem down to the fact that I'm not getting any CPU time for a substantial (at least up to 500 milliseconds) amount of time even though I'm using rtprio and there is nothing else that should be running. For years I've said that Unix is not a RTOS. For my application I think I can get by with FreeBSD. Your application sounds like it is more critical RT and I would recommend you go with a RTOS. In regards to your question of why 0.100 seconds is so common, FreeBSD uses a 10msec quantum. I suspect if you change kern.quantum to some other value then the other value will become more common. Let me know if you find some way that helps the latency. -- ======================================================================= Life is short. | Craig Spannring Ski hard, Bike fast. | cts@internetcds.com --------------------------------+------------------------------------ Any sufficiently perverted technology is indistinguishable from Perl. ======================================================================= To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message