"dev" <dev-boun...@openvswitch.org> wrote on 08/05/2016 10:51:38 PM:
> From: Nirapada Ghosh/San Jose/IBM@IBMUS > To: dev@openvswitch.org > Date: 08/05/2016 10:52 PM > Subject: [ovs-dev] [PATCH V14] Function tracer to trace all function calls > Sent by: "dev" <dev-boun...@openvswitch.org> > > From: Nirapada Ghosh <ngh...@us.ibm.com> > > In some circumstances, we might need to figure out where in > code, the CPU time is being spent most, so as to pinpoint > the bottleneck and thereby resolve it with proper changes. > Using '-finstrument-functions' flag, that can be achieved, and > this patch exactly does that. > > There is a python file [generate_ft_report.py] with the patch, > that may be used to convert this trace output to a human readable > format with symbol names instead of address and their execution > times. This tool uses addr2line that expects the executable to > be built with -g flag. > > To enable this feature, ovs needs to be configured with > "--enable-ft" command line argument [i.e. configure --enable-ft] > > This feature logs the tracing output to log files, > that is set using "ovs-appctl vlog/trace <filename>" command. > "ovs-appctl vlog/trace off" turns the logging off. > > The feature uses the hooks GNU-C provides when compiled with > -finstrument-functions flag, we just have to implement > them. What it means is, once you compile the code with --enable-ft > option, function calls are going to be routed to the tracing routine > anyways. In other words, even if we do disable tracing, the extra calls would > be happening though with very less CPU overhead, because the calls > would return right away. The initialization call [ constructor ] happens > even before main() is invoked, so no chance of completely disabling > tracing when configured with --enable-ft. So, unless you intend on debugging > a module in OVS, this option would better be turned off by default. > > It is intended to be used for debugging purposes only. > > Signed-off-by: Nirapada Ghosh <ngh...@us.ibm.com> > --- Ben, as an FYI, I've delegated this patch to myself in patchworks. I'll pass it along once I'm done (assuming that I'm happy)... _______________________________________________ dev mailing list dev@openvswitch.org http://openvswitch.org/mailman/listinfo/dev
