Re: 33% speed up in CC Mode scrolling.

[Alan Mackenzie <acm@muc.de>]

Hello, Martin.

On Mon, Jun 27, 2016 at 07:28:55PM +0200, martin rudalics wrote:
>  > font-lock-maximum-decoration  elapsed  average
>  > 3                             1.999    0.012
>  > 2                             1.765    0.010
>  > 1                             1.466    0.009

>  > In comparison the optimized build with ‘font-lock-maximum-decoration’ 3
>  > gets me:

>  > 3                             0.409    0.002

> These tests actually time scrolling only so they are misleading.  Using
> the modified attached file the results below are more accurate: R stands
> for the release branch, M for master, and O for an optimized build of
> master.  The following number is the ‘font-lock-maximum-decoration’
> value - 1, 2 or 3.  So R3 stands for the release branch with decoration
> level 3.  The second column is the elapsed, the third the average time.

> R3     109.61000000  0.6485798816
> M3      79.62599999  0.4711597633
> O3      11.516       0.0681420118
> R2      23.71799999  0.1403431952
> M2      25.35900000  0.1500532544
> R1      19.32799999  0.1143668639
> M1      20.406       0.1207455621

> So there is a significant speed up from R3 to M3 .....

This is the 33% speedup of the Subject: line.

> ....., and the speed up of M3 to M2 is by a factor of 3 approximately.

I see this, too.  The point is that fontification can hardly go faster
than level 1, which is mainly just syntactic fontification (i.e. strings
and comments).  The difference between levels 2 and 1 is probably small
enough that one might as well use level 2.

> With decoration levels 2 and 1 master is slightly slower than the
> release branch here.

I should keep an eye on this to make sure "slightly" is as far as it
goes.  It is interesting that the optimised compilation wins as much as
a factor of ~7.

My timing on this is (M-x foofoo on .../src/frame.c):

O3        7.1140785890  0.0817710182
Q3        8.939460839   0.1027524234

, where "Q3" is an optimised build from the release branch.

> martin

-- 
Alan Mackenzie (Nuremberg, Germany).