[Bug 162651] kded re-reads files every second

[Launchpad Bug Tracker]

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It seems that an instance of the KDE Daemon, kded, re-reads certain files 
every second. This leads to wasted CPU time, and less chance of 
power saving on laptops.

The following is a piece of an strace, which demonstrates the cycle:

fstat64(11, {st_mode=S_IFREG|0600, st_size=7558, ...}) = 0
munmap(0xb6033000, 7558)                = 0
rt_sigaction(SIGBUS, {SIG_DFL}, NULL, 8) = 0
close(11)                               = 0
stat64("/home/chrivers/.kde/share/config/kcmlaptoprc", {st_mode=S_IFREG|0600, st_size=1692, ...}) = 0
stat64("/etc/kde3/kcmlaptoprc", 0xbff493f8) = -1 ENOENT (No such file or directory)
stat64("/usr/share/kubuntu-default-settings/kde-profile/default/share/config/kcmlaptoprc", {st_mode=S_IFREG|0644, st_size=520, ...}) = 0
open("/usr/share/kubuntu-default-settings/kde-profile/default/share/config/kcmlaptoprc", O_RDONLY|O_LARGEFILE) = 11
fstat64(11, {st_mode=S_IFREG|0644, st_size=520, ...}) = 0
fstat64(11, {st_mode=S_IFREG|0644, st_size=520, ...}) = 0
mmap2(NULL, 520, PROT_READ, MAP_PRIVATE, 11, 0) = 0xb6034000
fstat64(11, {st_mode=S_IFREG|0644, st_size=520, ...}) = 0
rt_sigaction(SIGBUS, {0xb7839090, [], SA_ONESHOT}, {SIG_DFL}, 8) = 0
rt_sigprocmask(SIG_BLOCK, NULL, [], 8)  = 0
fstat64(11, {st_mode=S_IFREG|0644, st_size=520, ...}) = 0
munmap(0xb6034000, 520)                 = 0
rt_sigaction(SIGBUS, {SIG_DFL}, NULL, 8) = 0
close(11)                               = 0
open("/home/chrivers/.kde/share/config/kcmlaptoprc", O_RDONLY|O_LARGEFILE) = 11
fstat64(11, {st_mode=S_IFREG|0600, st_size=1692, ...}) = 0
fstat64(11, {st_mode=S_IFREG|0600, st_size=1692, ...}) = 0
mmap2(NULL, 1692, PROT_READ, MAP_PRIVATE, 11, 0) = 0xb6034000
fstat64(11, {st_mode=S_IFREG|0600, st_size=1692, ...}) = 0
rt_sigaction(SIGBUS, {0xb7839090, [], SA_ONESHOT}, {SIG_DFL}, 8) = 0
rt_sigprocmask(SIG_BLOCK, NULL, [], 8)  = 0
fstat64(11, {st_mode=S_IFREG|0600, st_size=1692, ...}) = 0
munmap(0xb6034000, 1692)                = 0
rt_sigaction(SIGBUS, {SIG_DFL}, NULL, 8) = 0


After approximately these many system calls, the exact same set
of calls are performed again, this re-reading the file. On a top(1), 
it's clearly visible that the kded uses a lot of time:

 5660 chrivers  15   0 41184 6400 4540 S  0.7  0.6  20:21.07 kded

Only kcryptd and xorg uses more than kded here!

** Affects: kdelibs (Ubuntu)
     Importance: Undecided
         Status: New

-- 
kded re-reads files every second
https://bugs.edge.launchpad.net/bugs/162651
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