Re: [Libunwind-devel] Backtrace performance on x86-64 based on Dwarf info

[Milian Wolff]

On Wednesday 04 June 2014 15:45:52 Milian Wolff wrote:
> On Wednesday 04 June 2014 15:28:10 Milian Wolff wrote:
> > On Tuesday 03 June 2014 09:53:02 Arun Sharma wrote:
> > > On Tue, Jun 3, 2014 at 6:18 AM, Milian Wolff <address@hidden> wrote:
> > > > To me that does not look like a failure :)
> > > 
> > > Yeah, I'll fix up the test too unless this breaks any of the stuff
> > > Lassi may be aware of.
> > 
> > I just noticed an issue with adding the simple !bdp check to Gtrace.c - it
> > leads to an early cancellation of the backtraces when sections without
> > debug symbols are encountered:
> > 
> > ...
> > 0x7f868820167a QMapData::node_create(QMapData::Node**, int, int)
> > /usr/lib/libQtCore.so.4
> > 0x7f86886ea740 ? /usr/lib/libkdecore.so.5
> > 0x7f86886fa986 ? /usr/lib/libkdecore.so.5
> > 0x7f86886fafc4 ? /usr/lib/libkdecore.so.5
> > 0x7f86886e4320 ? /usr/lib/libkdecore.so.5
> > 0x7f86886e4731 KConfig::KConfig(QString const&, QFlags<KConfig::OpenFlag>,
> > char const*) /usr/lib/libkdecore.so.5
> > ... more useful information here
> > 
> > becomes
> > 
> > ...
> > 0x7f868820167a QMapData::node_create(QMapData::Node**, int, int)
> > /usr/lib/libQtCore.so.4
> > 
> > For my use-case this is unacceptable. Any idea what might be going on
> > here?
> > Any information you would like me to get you?
> 
> Note: this patch seems to work just fine for me, but I don't know whether it
> breaks anything else... At least the tests work just fine with it! So, do
> you see any other problems with it?

Hm no that one is not enough apparently. It still triggers too many slow paths 
ending up in the initial bottleneck I found.

Really, so far only the check for a null rip seems to work both fast and 
reliable in my case... Any ideas on how to proceed now?

Bye
-- 
Milian Wolff
address@hidden
http://milianw.de