Looked at this issue some more.
/usr/bin/kslideshow.kss has many transition-effects between photos.
Which transitions are being used is not a configurable option so you get all of
them.
Most of the transitions are lightweight and finish in a second or two.
Some of the transitions are complex and take very long to complete.
When one of these more complex transitions which take a very large
number of seconds to finish kicks in (can be a minute or more), the
computer becomes sluggish.
The worst offender is a transition that does a random almost pixel-by-
pixel rendering of the new photo superimposed on the previous photo.
While this is going on an strace of the kslideshow.kss process shows a
tight loop of poll() and writev() system calls.
here's short sample, there are many of these every second.
poll([{fd=6, events=POLLIN|POLLOUT}], 1, -1) = 1 ([{fd=6, revents=POLLOUT}])
writev(6, [{"H\2\376\331s\336\5\5t\336\5\5X\2]\0\0\0G\1\0\30\0\0", 24},
{"\0\0\0\377\0\0\0\377\0\0\0\377\0\0\0\377\0\0\0\377\0\0\0\377\0\0\0\377\0\0\0\377"...,
223200}, {"", 0}], 3) = 128000
poll([{fd=6, events=POLLIN|POLLOUT}], 1, -1) = 1 ([{fd=6, revents=POLLOUT}])
writev(6,
[{"\33\257\377\377\33\256\377\377\26\253\377\377\26\251\376\377\34\255\376\377+\277\377\377-\305\377\3772\320\377\377"...,
95224}, {"", 0}], 2) = 95224
poll([{fd=6, events=POLLIN|POLLOUT}], 1, -1) = 1 ([{fd=6, revents=POLLOUT}])
writev(6,
[{"<\2\2\0t\336\5\5\230\4\5\0u\336\5\5s\336\5\5!\1\0\0\0\0\0\0>\2\7\0"...,
128},
{"\0\0\0\377\0\0\0\377\0\0\0\377\0\0\0\377\0\0\0\377\0\0\0\377\0\0\0\377\0\0\0\377"...,
261600}, {"", 0}], 3) = 128000
poll([{fd=6, events=POLLIN|POLLOUT}], 1, -1) = 1 ([{fd=6, revents=POLLOUT}])
kslideshow.kss is in the package kdeartwork. I did a apt-get source and looked
at the sources.
I believe the source is kdeartwork-4.7.2/kscreensaver/kdesavers/slideshow.cpp
but not 100% sure.
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https://bugs.launchpad.net/bugs/878621
Title:
Screensaver takes too long to exit after unlock
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