Re: Ups 3.37-bet4 taking larges amounts of CPU time

From: Flemming Madsen (
Date: Wed Jan 09 2002 - 10:09:56 GMT

I have always wondered why Ups would take up all CPU on linux
while the target is running.  In my experience that _is_ happening.

Why not usleep() for maybe 10ms for each iteration. That would most
probably take the CPU load down to a sub-percent level.

wkr /Flemming

Tom Hughes wrote:
> In message <>
> wrote:
> > I have just built the latest beta of UPS (3.37 beta4) for an x86
> > machine running RedHat 7.1 and the first thing that struck me was
> > that UPS uses 20-25% of the cpu whilst the process being debugged is
> > running.. This compares to < 1% usage by ups version 3.36 (admittedly
> > the 3.36 version is running under redhat 6.2). Is the new ups doing
> > more? and if so can I disable this?
> I can reproduce this, and I understand why it is happening, but I don't
> see anything different with 3.36 in my environment - the code in question
> is the same and the result (high cpu utilisation) is also the same.
> The reason is that ptrace_wait_for_target() in ao_ptrace.c is trying
> to watch both for a change of state in the target process and for the
> user pressing the stop button and it is doing so by busy waiting,
> testing for each change in turn.
> Fixing it would mean that one of the notifications would have to be
> made to happen asynchronously so that a blocking wait could then be
> done on the other notification.
> Tom
> --
> Tom Hughes (
> Software Engineer, Cyberscience Corporation

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