LibreOffice Impress Becoming Very Slow After Copy/Paste

LibreOffice Impress version 5.1 and 5.2 for Linux kernel 4.7 becomes extremely slow, if one copies some slides multiple times. This behaviour can be reproduced on laptops, machines with and without graphic card. For example, take a random presentation and copy one slide 20 times by pressing ctrl-v. The slides don’t have to be complex — they can be very simple without pictures or graphics of any kind.

LibreOffice Impress is the PowerPoint clone of LibreOffice / OpenOffice.

There are multiple hints when searching for this in Google, see for example Copy/ Pasting and Moving Slides become slow as presentation is becoming more complex.

The effect is that a single core is 100% busy for seconds or even a full minute. It is unknown why the load is not distributed evenly to the other cores, which are free to use, see top output below. It is also unknown what exactly takes so much CPU time to compute.

top - 21:08:44 up  1:09, 11 users,  load average: 0.27, 0.27, 0.35
Tasks: 210 total,   3 running, 207 sleeping,   0 stopped,   0 zombie
%Cpu0  :   4.6/1.3     6[|||                                                  ]
%Cpu1  :   0.0/0.0     0[                                                     ]
%Cpu2  :   3.3/0.0     3[||                                                   ]
%Cpu3  :   1.3/0.0     1[|                                                    ]
%Cpu4  :   2.0/0.7     3[|                                                    ]
%Cpu5  :   1.3/1.3     3[||                                                   ]
%Cpu6  : 100.0/0.0   100[|||||||||||||||||||||||||||||||||||||||||||||||||||||]
%Cpu7  :   0.0/0.0     0[                                                     ]
GiB Mem :  9.9/15.623   [                                                     ]
GiB Swap:  0.0/0.000    [                                                     ]

  PID USER      PR  NI    VIRT    RES  %CPU %MEM     TIME+ S COMMAND           
    1 root      20   0  131.9m   6.4m   0.0  0.0   0:02.43 S systemd           
  233 root      20   0   63.9m   9.0m   0.0  0.1   0:00.34 S  `- systemd-journ+
  258 root      20   0   35.3m   4.0m   0.0  0.0   0:00.14 S  `- systemd-udevd 
  411 root      20   0   89.9m   1.5m   0.0  0.0   0:00.00 S  `- lvmetad       
  449 root      20   0   37.6m   4.6m   0.0  0.0   0:00.04 S  `- systemd-logind
  450 avahi     20   0   40.2m   3.0m   0.0  0.0   0:00.01 S  `- avahi-daemon  
  452 avahi     20   0   40.2m   0.3m   0.0  0.0   0:00.00 S      `- avahi-dae+
  451 dbus      20   0   32.5m   3.8m   0.0  0.0   0:00.14 S  `- dbus-daemon   
  453 root      20   0  347.9m  14.0m   0.0  0.1   0:00.32 S  `- NetworkManager
  486 root      20   0  190.2m   4.6m   0.0  0.0   0:02.79 S  `- slurmd

Interestingly, LibreOffice 4.2.8.2 on Ubuntu 14.04.3 LTS (kernel 3.13.0-74) does not exhibit this behaviour. As has been said a number of times, newer is not better.

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