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

From: Tom Hughes (
Date: Wed Jan 09 2002 - 09:53:45 GMT

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 Hughes (
Software Engineer, Cyberscience Corporation

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