From: Kevin Buettner <kevinb@redhat.com>
To: rda@sources.redhat.com
Subject: Re: [RFC] Improve performance of multi-threaded debugging
Date: Wed, 14 Sep 2005 22:31:00 -0000 [thread overview]
Message-ID: <20050914153131.4924147d@ironwood.lan> (raw)
In-Reply-To: <20050914220851.GA12788@nevyn.them.org>
On Wed, 14 Sep 2005 18:08:51 -0400
Daniel Jacobowitz <drow@false.org> wrote:
> On Wed, Sep 14, 2005 at 03:04:39PM -0700, Kevin Buettner wrote:
> > As things stand now, the thread list is fetched each time rda checks
> > the status of the program. This doesn't sound like such a burden until
> > you realize that some decent sized data structures are read via the
> > ptrace() interface. On slower machines, it can take a significant amount
> > of time to single step or continue primarily due to this overhead.
> >
> > The patch below fetches the thread list only when it knows for certain
> > that something has changed.
> >
> > The only fly in the ointment is that the signal based event model only
> > knows about thread creation, but not about thread death. So it won't
> > catch thread death until some new thread is created. I'm not sure
> > what the implications of this are in practice.
>
> You may run a risk of not noticing when a thread is destroyed
> and then a new thread is created with the same thread ID - which NPTL
> does all the time.
>
> Other than that I haven't looked at rda enough to comment. I'm not
> sure what you mean about not knowing about thread death; you ought to
> be notified about thread death (A) via TD_* and (B) via wait, except on
> some broken RH 2.4 kernels.
I have the TD_ case taken care of. My patch didn't address the wait() case
though.
Thanks for your comments!
Kevin
next prev parent reply other threads:[~2005-09-14 22:31 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2005-09-14 22:04 Kevin Buettner
2005-09-14 22:09 ` Daniel Jacobowitz
2005-09-14 22:31 ` Kevin Buettner [this message]
2005-09-16 20:13 ` Jim Blandy
2005-09-16 20:20 ` Jim Blandy
2005-09-16 20:49 ` Kevin Buettner
2005-09-17 0:19 ` Jim Blandy
2005-11-04 21:16 ` Kevin Buettner
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