Re: State of the overlay tree branch?

[Sebastian Sturm]

>
> It should do that without you asking.  I mean, it won't show you
> `goto-char` and `point-min` kind of things since these are "inlined"
> (actually turned into their own byte-code), but `count-lines` should
> definitely be there.
>
>>               - let 
18368  86%
>>                  line-number-at-pos 
18348  86%
>
> It's very odd that there's no `count-lines` down here (and `count-lines`
> is a perfectly normal Elisp function that's not inlined or otherwise
> treated specially), since it should be where most of the time is spent!

when first evaluating simple.el as Eli suggested, the profiler indeed 
shows that pretty much all time is spent somewhere within `count-lines`. 
Unfortunately the patch didn't seem to help though I'll double-check at 
home (also, it seemed to improve baseline performance, but I'm not sure 
if I should regard that as a random fluctuation, will need to do more 
measurements).
Also, this time even the first measurement with a small number of 
overlays was extremely slow, not sure what to make of that.

In general however, the trend seems clear to me --- for this one file, 
overlays hurt `line-number-at-pos` performance very much, except when 
using the noverlay branch.
Are there other things I should look for in my file that might 
negatively affect performance (strange codepoints or anything else that 
might perhaps upset `buf_charpos_to_bytepos`)?

baseline (emacs-27 master #667cdf42..., approx. 5-10 overlays created by 
flycheck):
iteration 1: 0.012696
iteration 2: 0.002595
iteration 3: 0.002606
iteration 4: 0.002601
iteration 5: 0.002649
iteration 6: 0.002605
iteration 7: 0.002594
iteration 8: 0.002601
iteration 9: 0.002603
iteration 10: 0.002601
iteration 11: 0.002606
iteration 12: 0.002626
iteration 13: 0.002603
iteration 14: 0.002642
iteration 15: 0.002599
iteration 16: 0.002598
iteration 17: 0.002600
iteration 18: 0.002601
iteration 19: 0.002599
iteration 20: 0.002608

emacs-27 master, approx. 6200 overlays created by (test-highlight)
iteration 1: 0.022795
iteration 2: 0.015560
iteration 3: 0.015697
iteration 4: 0.015913
iteration 5: 0.015894
iteration 6: 0.016063
iteration 7: 0.015928
iteration 8: 0.015890
iteration 9: 0.015278
iteration 10: 0.015515
iteration 11: 0.015327
iteration 12: 0.015326
iteration 13: 0.015574
iteration 14: 0.015319
iteration 15: 0.015370
iteration 16: 0.015354
iteration 17: 0.015333
iteration 18: 0.015312
iteration 19: 0.015481
iteration 20: 0.015411

emacs-27 master + patch "distance+10", ~10 overlays created by flycheck:
iteration 1: 0.002938
iteration 2: 0.001132
iteration 3: 0.000550
iteration 4: 0.000468
iteration 5: 0.000470
iteration 6: 0.000451
iteration 7: 0.000449
iteration 8: 0.000451
iteration 9: 0.000450
iteration 10: 0.000449
iteration 11: 0.000448
iteration 12: 0.000452
iteration 13: 0.000451
iteration 14: 0.000443
iteration 15: 0.000448
iteration 16: 0.000443
iteration 17: 0.000444
iteration 18: 0.000445
iteration 19: 0.000445
iteration 20: 0.000445

emacs-27 master + patch "distance+10", ~6200 overlays created by 
(test-highlight):
iteration 1: 0.019673
iteration 2: 0.014469
iteration 3: 0.014491
iteration 4: 0.014430
iteration 5: 0.014493
iteration 6: 0.014704
iteration 7: 0.014741
iteration 8: 0.014536
iteration 9: 0.014433
iteration 10: 0.014469
iteration 11: 0.014429
iteration 12: 0.014509
iteration 13: 0.014484
iteration 14: 0.014487
iteration 15: 0.014524
iteration 16: 0.014449
iteration 17: 0.014501
iteration 18: 0.014469
iteration 19: 0.014429
iteration 20: 0.014507

noverlay branch (#886933...), ~10 overlays:
iteration 1: 0.002370
iteration 2: 0.001191
iteration 3: 0.001189
iteration 4: 0.001162
iteration 5: 0.001095
iteration 6: 0.001096
iteration 7: 0.000522
iteration 8: 0.000531
iteration 9: 0.000369
iteration 10: 0.000365
iteration 11: 0.000365
iteration 12: 0.000366
iteration 13: 0.000365
iteration 14: 0.000380
iteration 15: 0.000367
iteration 16: 0.000365
iteration 17: 0.000365
iteration 18: 0.000365
iteration 19: 0.000363
iteration 20: 0.000368

noverlay branch, ~6200 overlays:
iteration 1: 0.001878
iteration 2: 0.001831
iteration 3: 0.001838
iteration 4: 0.001826
iteration 5: 0.001027
iteration 6: 0.000722
iteration 7: 0.000531
iteration 8: 0.000479
iteration 9: 0.000480
iteration 10: 0.000479
iteration 11: 0.000479
iteration 12: 0.000479
iteration 13: 0.000478
iteration 14: 0.000479
iteration 15: 0.000478
iteration 16: 0.000478
iteration 17: 0.000482
iteration 18: 0.000479
iteration 19: 0.000480
iteration 20: 0.000476