On Mon, 2 Feb 2009, Roland McGrath wrote: > > I thought we were going to enable these in rawhide since the e1000 > > EEPROM problem was fixed: > > > > CONFIG_FUNCTION_TRACER (was CONFIG_FTRACE) > > CONFIG_DYNAMIC_FTRACE > > Last I knew this still uses -pg and implies -fno-omit-frame-pointer. > This probably kills performance somewhat, and more importantly during a > rawhide debug-kernel phase, might change the corners of compiler behavior > that we're checking vs what we'd want in a production kernel. The performance hit by -fno-omit-frame-pointer depends on the which hardware you are running. I've been told by Arjan that the latest x86 hardware has negligible performance hit on this feature. But with this on, you can enable kernel function tracing at runtime. And this is a very powerful tool. This might be something to discuss, where we may sacrifice a bit of power for the ability of dynamic tracing. Benchmarks welcome ;-) -- Steve _______________________________________________ Fedora-kernel-list mailing list Fedora-kernel-list@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/fedora-kernel-list
