Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: utzoo!utgpu!water!watmath!clyde!rutgers!cmcl2!brl-adm!adm!mankin@gateway.mitre.ORG From: mankin@gateway.mitre.ORG Newsgroups: comp.unix.wizards Subject: Kernel Timings with MicrovaxII Message-ID: <10646@brl-adm.ARPA> Date: Thu, 3-Dec-87 11:14:14 EST Article-I.D.: brl-adm.10646 Posted: Thu Dec 3 11:14:14 1987 Date-Received: Sun, 6-Dec-87 17:11:34 EST Sender: news@brl-adm.ARPA Lines: 34 Hi, folks, I am working on IP-level performance in 4.3 BSD on a MicrovaxII. The CPU is a 630-Q-A, since we bought the system over 2 years ago. The operating system is pure Berkeley 4.3. My question is about the real-time clock resolution. The hardware manual does not cover the 630, but analogy to the 750 (and a good letter to this list by Chris Torek back in August) got me hoping it would be possible to read times at a resolution of microseconds from the 630's Interval Count Register. I didn't see anything to contradict this in the 4.3 source code. Alas, experiment and our DEC representative have at last revealed that I will never read times of less than 10 milliseconds from this ICR. Now, in the latest Proceedings of the ACM Symposium on Operating Systems Principles (SOSP-11), there are at least two articles where a MicrovaxII was used to do performance timings. Jeff Mogul et al includes figures like 1.77 milliseconds for the kernel to process a received IP packet. Liskov et al give times such as that required for a minimal system call (200 microseconds). (By the way, their articles are very juicy and interesting). Do you get such timings only by doing thousands of identical operations and measuring the aggregate time? I've found out from DEC about a programmable real-time clock for the MicrovaxII, the KWV-11-C. Its cost is quite low, but they do not have a driver for it outside an expensive package called LabStar. Could anyone point me to a UNIX driver, or to the good techniques other than aggregate measurements for using the MicrovaxII for kernel timings? AM