Re: performance improvements

[John W. Eaton]

On 9/3/19 8:14 PM, Rik wrote:
> On 09/03/2019 03:39 PM, John W. Eaton wrote:

> Finally, I suspect you're right about the unwind_protect blocks.  When I
> ran with perf there were indications in the stack that unwind_protect was
> consuming some time, but it was hard to figure out exactly how it was
> happening.
>
> > So in the vast majority of cases, we only have one action to perform, so
> > creating a stack and using virtual function dispatch doesn't make much
> > sense.  We could speed this up a lot just by defining a few special case
> > classes that save and restore single values or call a single function
> > (and with lambda capture, we just need a single simple interface).  I'll
> > take a look at doing that soon.
>
> I'll re-run under perf to see what the new code hotspots are.  By knocking
> down the overall running time we will get a magnification effect for the
> remaining issues.

I pushed some more changes in an attempt to improve the performance of 
single unwind-protect actions:

  http://hg.savannah.gnu.org/hgweb/octave/rev/2f8428b61bd6
  http://hg.savannah.gnu.org/hgweb/octave/rev/25627c524ad8
  http://hg.savannah.gnu.org/hgweb/octave/rev/d171d356767b

Now I see the following timings on my system:

          bm_assign     bm_toeplitz

   3.2.4:   0.19735      11.278
   3.4.3:   0.17148       9.2246
   3.6.4:   0.21437       9.5798
   3.8.2:   0.25326      15.447
   4.0.3:   0.51134      27.710
   4.2.2:   0.53206      26.772
   4.4.1:   1.5782       31.758
   5.1.0:   1.7119       36.593
  before:   1.9624       30.399
     now:   0.62128      18.524

The "before" line is changeset 64289bf338da:

  user:        John W. Eaton <address@hidden>
  date:        Wed Aug 14 00:19:34 2019 -0400
  summary:     use separate variable for interrupting command editor 
event loop (bug #56738)

I think that is prior to any changes related to this issue.

Could you try another profiling run with these changes?  The 
convert_to_const_vector function uses unwind_protect, so the latest 
changes might have made a difference.

jwe