Comment 35 for bug 1034999

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.