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From: daniel@sdl.mdcbbs.com
Newsgroups: comp.unix.internals
Subject: Scheduling of processes, and timers
Message-ID: <1991Jun13.141021.1@sdl.mdcbbs.com>
Date: 13 Jun 91 13:10:21 GMT
Organization: Shape Data Ltd. (McDonnell Douglas M&E, Cambridge UK)
Lines: 36
Nntp-Posting-Host: sldv16
Nntp-Posting-User: kretch


    
    I've written a program which interrupts another process every few
milliseconds and takes a copy of the stack. This information is later
processed to give profile information.

    I use sigitimer to wake myself up, and ptrace to interupt the other
process and take a copy of its stack. This has been developed on 
Sparcstations running SunOs4.1, but should work on other Unix variants.
   
Anyway I have two problems :-
                           
 1) Scheduling, the process doing the interrupting appears to get 
    scheduled during system calls in the process being monitored. In
    particular there is a very large bias to ioctl.

        Is scheduling likely to take place at system calls ?
        Is there a way round this if this is so ?
        Do I just give up and use gprof ?

 2) The timer resolution on a Sparc 2 is 100Hz, and as it is an
    umpty frumpt MIP box even if I cross the first hurdle I'll miss
    large chunks of code.

        Is there any other timer available on Sparcstations ?

Thanks

    Daniel Dignam
    daniel@sdl.mdcbbs.com

-- 
Daniel Dignam                           Shape Data Limited (McDonnell Douglas)
 Internet: daniel@sdl.mdcbbs.com           46 Regent Street
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