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Re: gdb/457: GDB runs slow (internal doco needed) (FAQ)


The following reply was made to PR gdb/457; it has been noted by GNATS.

From: Andrew Cagney <ac131313@redhat.com>
To: gdb-gnats@sources.redhat.com
Cc:  
Subject: Re: gdb/457: GDB runs slow (internal doco needed) (FAQ)
Date: Thu, 28 Nov 2002 13:50:19 -0500

 http://sources.redhat.com/cgi-bin/gnatsweb.pl?cmd=view%20audit-trail&database=gdb&pr=457
 
 For an update on the thread problem, see:
 
 http://sources.redhat.com/ml/gdb/2002-11/msg00316.html
 
 GDB wasn't so much slow, as catatonic.
 
 Turns out that GDB was doing several million ptrace() memory reads for 
 roughly 1000 single steps.
 
 Given that, the overhead of stopping/starting threads, or fetching 
 registers, is seriously in the noise.
 
 While things have been improved, more improvement is possible.
 
 The one post mortem comment here, I think, is that (as people teaching 
 one how to use profile tools are quick to remind us), it isn't what you 
 know but what you don't know that is important.  The numbers returned by 
 profile, for instance, were singularly misleading :-(
 
 Andrew
 


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