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Path: sserve!manuel!munnari.oz.au!mips!mips!swrinde!cs.utexas.edu!uunet!newsgate.watson.ibm.com!yktnews!admin!w2chase From: w2chase@watson.ibm.com (Craig Chase) Newsgroups: comp.unix.bsd Subject: Re: High Resolution getrusage Keywords: FYI Message-ID: <1992Aug06.134645.30687@watson.ibm.com> Date: 6 Aug 92 13:46:45 GMT References: <1992Aug3.055929.23488@Unibase.SK.CA> <1992Aug3.145858.5601@rwwa.COM> <1992Aug4.174041.6897@Unibase.SK.CA> <15n3pnINN66t@agate.berkeley.edu> Sender: w2chase@watson.ibm.com (Chase C) Distribution: usa Organization: Electrical Engineering, Cornell University, Ithaca NY Lines: 29 Disclaimer: This posting represents the poster's views, not necessarily those of IBM Nntp-Posting-Host: tweetie.watson.ibm.com Well, in case anyone is losing sleep worrying about how to get to-the-microsecond timings on Unix (please don't sue me AT&T, I promise not to say "Unix" in public again) machines, I've learned that that IBM RS/6000 has hardware support for collecting trace data. AIX has a device driver that buffers trace info in the kernel memory until it's full and then writes it to disk. No, it's not BSD, but what can you do when you work (temporarily) for big blue? Yes, collecting a trace does modify performance (affecting cache, paging, scheduling behavior, etc) but any monitoring system will be intrusive in some way, and with hardware support it hopefully won't be too bad. Yes, this means I have to reconstruct the timings for events in my simulated multiprocessor in a post-mortem pass. Tracing is not limited to the activities of a single process, but the trace data does include operating system events such as rescheduling a new process. It's possible to reconstruct with some reasonable accruacy how much time your process took, it is perhaps non-trivial (as you have to identify and elminate time spent servicing page faults, network interrupts, etc. etc. etc.) Other machines may have similar capabilities, I've been lead to believe that the Convex machines have very nice timing facilities. (Anyone have a convex I can borrow for a semester or two?). Craig