[Libreoffice-bugs] [Bug 108560] EDITING: Slow Edit or Open Large Cells

[bugzilla-daemon at bugs.documentfoundation.org]

https://bugs.documentfoundation.org/show_bug.cgi?id=108560

--- Comment #12 from Francewhoa <francewhoa+bugs.documentfoundation.org at ubertus.ca> ---
Test results:
• File in comment #8 is 129 lines, 773 characters with spaces, 0.7 kB size.
  Results in ~2 seconds lag per action. Calc IS usable :)

• File in comment #9 is 235 lines, 1,409 characters with spaces, 1.4 kB size. 
  Results in ~11 seconds lag per action. Calc is NOT usable :(

• File in comment #10 is 470 lines, 2,819 characters with spaces, 2.8 kB size. 
  Results in ~100 seconds lag per action. Calc is NOT usable :(

• File in comment #11 is 940 lines, 5,639 characters with spaces, 5.6 kB size. 
  Results in ~780 seconds lag per action. Calc is NOT usable :(

The lag is both correlated with the number of lines and exponential with the
number of lines. In other words, the lag per action ranges from ~2 seconds with
129 lines to more than 13+ minutes lag with 940+ lines, and so on and
exponential.

Notice that the results above are sorted top down in lag time results. The last
result in comment #11 is ~780 seconds lag which means ~13 minutes lag. That is
longggggg for just one action with simple text without calculation and minimum
formatting. So long I could feel my beard growing and I needed a second shave
after the lag, LOL (joke ;) Also during that long lag period all LibreOffice
tools are frozen and not usable. So the users can not use Calc, Write, or any
other LibreOffice tool. In my personal experience, after 5 to 10 seconds lag
most users feel the software crashed, froze, or is not working, most user don't
know it is a lag.

All those tests are using LibreOffice 5.2.7.2. Steps to reproduce and details
in this ticket description above.

While testing, another thing I noticed is during the lag one CPU is used at
100%. If the computer as multiple CPUs, for example 8 CPUs, then each CPU is
used in turn at 100%. Roughly 2 to 3 seconds each at 100%. So one CPU always at
100%. That means users with fast CPU at 3+ GHz and 8+ CPU might not notice the
~2 seconds lag with the file in comment #8 at 129 lines. But users with slower
or less CPU(s) might face the challenge of having both their LibreOffice and
their full computer not usable during a longer lag.

If you try to reproduce this lag, I suggest to double check that you do at
least two actions on a large cell, not just one action. Because sometime when
using a freshly open and blank Calc spreadsheet, the first action is very fast
with a large cell. The lag is sometime triggered only with the second action
with a large cell, and all following actions. By "action" I mean action on a
large cell such as open, edit, or paste into.

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