Re: more on gdb server

Quality Quorum
2001-07-18T13:53:00Z

On Wed, 18 Jul 2001, Daniel Jacobowitz wrote:

> On Wed, Jul 18, 2001 at 03:40:57PM -0400, Quality Quorum wrote:
> > On 18 Jul 2001, J.T. Conklin wrote:
> >
> > > > > I know HP were once playing with ideas that would have eliminated any
> > > > > copying because they were finding memory read/write performance using
> > > > > ptrace (or what ever) lacking.
> > > >
> > > > I would suppose they had something truly unusual - debuggin is going with
> > > > the pace of human reaction to debugging events and I can hardly imagine
> > > > that network performance over local loop interface would be a factor here.
> > >
> > > Remember that GDB may be issuing many low level commands for each high
> > > level (CLI) command. For example, a single step or next command may
> > > issue several step instruction, fetch registers, and store registers
> > > commands. On some large programs, some interactive commands are
> > > beyond the interactive threshold (something like .3 seconds? I can't
> > > remember the commonly quoted figure), this additional overhead would
> > > only make it worse.
> > >
> > > Also note that oftentimes it's not a human driving the debugging
> > > session, but user defined functions that grovel through data
> > > structures, call inferior functions, etc.
> >
> > I still have hard time to beleive that there is an issue here.
>
> Consider software watchpoints, already almost uselessly slow. Consider
> single-stepping over a single line of code consisting of forty or four
> hundred machine instructions. There can be a significant overhead.

I would say that it is a stong case to make protocol a tiny little bit
more rich :).

> Daniel Jacobowitz Carnegie Mellon University

Thanks,

Aleksey