From mboxrd@z Thu Jan 1 00:00:00 1970 X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on polar.synack.me X-Spam-Level: * X-Spam-Status: No, score=1.3 required=5.0 tests=BAYES_00,INVALID_MSGID, MSGID_RANDY autolearn=no autolearn_force=no version=3.4.4 X-Google-Language: ENGLISH,ASCII-7-bit X-Google-Thread: 103376,71b19e01eae3a390 X-Google-Attributes: gid103376,public From: dennison@telepath.com Subject: Re: delay until and GNAT - expand Date: 1999/05/11 Message-ID: <7h9j77$61l$1@nnrp1.deja.com>#1/1 X-Deja-AN: 476609362 References: <7gpukr$s82$1@nnrp1.dejanews.com> <7grkbb$cee$1@nnrp1.deja.com> <7grvka$lc5$1@nnrp1.deja.com> <7h1e10$drg$1@nnrp1.deja.com> <7h830a$e4$1@nnrp1.deja.com> X-Http-Proxy: 1.0 x37.deja.com:80 (Squid/1.1.22) for client 204.48.27.130 Organization: Deja.com - Share what you know. Learn what you don't. X-Article-Creation-Date: Tue May 11 15:43:35 1999 GMT Newsgroups: comp.lang.ada X-Http-User-Agent: Mozilla/4.5 [en] (WinNT; I) Date: 1999-05-11T00:00:00+00:00 List-Id: In article <7h830a$e4$1@nnrp1.deja.com>, Robert Dewar wrote: > In article , > rracine@draper.com (Roger Racine) wrote: > > > I just did a little checking on Wind Rivers' web site, and I > > found, for the "MV167C" Motorola 68K board (they do not > > specify which chip or speed in the web page), "context > > switching requires only 3.8 microseconds". Not exactly 1 > > microsecond, but I got the order of magnitude correct. > > I would say this shows you likely got the order of magnitude > one off. Implementation of a delay involves more than a simple > context switch. As I say, we will measure the WR VXW speed > on a fast machine and see what we get. I am willing to bet > you are way off in the one microsecond estimate. Yes, it would > be nice if it were only one microsecond, but I am afraid we will > not see it. Anyway, let's wait till we can get some data here. I'm not sure *exactly* what you were hoping to measure. However, I happen to have an old Windview log here of a program that uses "delay until" for scheduling. It was taken on a PII-400 PC. What I am seeing is that "interrupt 0", the clock interrupt, takes about 11 micro seconds. Then the slighly misnamed "idle" task continues to execute for about 11 micros. Then my Ada task begins. Where in there my Ada code starts executing again rather than vxWorks system calls, I cannot tell with Windview. But all totaled that is about 22 microseconds from the clock tick at which the delay expired to the time my Ada task's context was switched to. Note that this is with the Pentium II fix that is in Tornado II (The fix prevents a rather bogous and very time consuming cache invalidation, as I understand it). Before the fix we were seeing times of 19 and 50 micros for a total of about 70 respectively. -- T.E.D. --== Sent via Deja.com http://www.deja.com/ ==-- ---Share what you know. Learn what you don't.---