Noted slowness in profile loading with binutils 2.37

[Alan Modra]

On Tue, Feb 08, 2022 at 09:44:58AM -0800, Alexander Lindsay via Binutils wrote:
> Hi all,
> 
> I recently experienced a slow-down in profile loading by the tool pprof,
> and I believe I've boiled it down to changing from previous versions of
> binutils to binutils version 2.37. Timings of profile loading are
> documented on the pprof ticket I originally opened here:
> https://github.com/google/pprof/issues/680#issuecomment-1032174210. I
> reproduce them below:
> 
> - binutils version 2.29.1: 1.1 seconds
> - binutils version 2.33.1: 1.1 seconds
> - binutils version 2.35.2: 6.8 seconds
> - binutils version 2.36.1: 6.5 seconds
> - binutils version 2.37: Still not loaded at 6 minutes
> 
> I think the relevant binutil tool here is addr2line. Does anyone have a
> quick idea for what may have caused the slow-down? I was thinking about
> doing a git bisect, but I figured it is probably way more efficient to
> contact the experts!

The "experts" here have made lots of changes in the time between 2.33
and 2.37.  It's hard to say which one might have caused the extreme
slowdown.  Bisection is the way to go.  I hope it doesn't turn out to
be one of the many patches made for fuzzed object files, which may
help security a tiny bit but in general don't result in a better
binutils.

-- 
Alan Modra
Australia Development Lab, IBM