Re: gdb symbol lookup very slow

[Antonio Cavallo <a dot cavallo at cavallinux dot eu>]

Hi,

thank you for the reply.


Andrew Burgess wrote:
> On 28/05/2014 8:59 AM, Antonio Cavallo wrote:
> > I'm having hard time debugging a (very large) C++ library under gdb (gdb
> > 7.7.1, gcc 4.8, binutils 2.22).
>
> Details of your target architecture / operating system /etc would be
> helpful.

the target is x86_64, it's centos (red hat 6.5) system;


> I suspect you've not mentioned something important :) In "normal"
> circumstances, once a breakpoint has been placed, and the program being
> debugged has been resumed, then there should be no time spent inside gdb.

The break point is "pending" because the library to be debugged is not 
loaded at the main debuggee startup.

> Are you by chance using conditional breakpoints?  Or stepping, or using
> some other commands?

After the gdb starts (gdb --args <myprogram> <arguments>) I simply set 
the breakpoint (pending) and run the application: at that point after 
2mins it reaches the breakpoint.

As test I've run the gdb --args <myprogram> <arguments> without the 
breakpoint and the app completes in under few seconds. So the 
performance hit might be due to the breakpoint (and the libraries loaded).


> The best thing would be to post a small example session, an annotate
> which commands you feel are taking longer than expected.  Also, you
> mention that you profiled gdb, assuming that it's not too large, making
> the profile data available might allow some more insight.

I'll grab all the info I can get out of it. In the meanwhile is there 
anything I can try to check what might cause that?

> Thanks for reporting this issue, and taking the time to investigate it.
>
> Andrew

Thanks
Antonio