Compile with -fno-omit-frame-pointer on x86_64?
jakub at redhat.com
Wed Nov 3 20:11:42 UTC 2010
On Wed, Nov 03, 2010 at 04:10:30PM -0400, Adam Jackson wrote:
> On Wed, 2010-11-03 at 19:58 +0100, Jakub Jelinek wrote:
> > On Wed, Nov 03, 2010 at 02:48:12PM -0400, Owen Taylor wrote:
> > > Basically summarizes the situation, and as far as I know nothing has
> > > changed ... with default compilation options, getting callgraph
> > > profiling on x86_64 really requires a DWARF unwinder in the kernel.
> > > Which seems unlikely to happen.
> > But that's the right thing to do.
> Sure, but so is a kernel debugger, and it's taken us over ten years to
> get one. I'm pretty okay with doing something wrong now if it gets me
> something usable for long enough to get something right later. I'll
> take 4% across the board if it helps me find the 20% that matters.
Most of the time you don't find the 20% improvements with profilers though,
so all we end up with is just slowing everything by 4%. Definitely a bad
idea, now that per core performance doesn't increase very much and most
programs aren't parallelized at all or just very badly.
More information about the devel