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List:       kde-bugs-dist
Subject:    Bug#26478: kmix busy waiting, burns cpu
From:       law () sgi ! com
Date:       2001-05-31 15:05:48
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Package: kmix
Version: unknown (using KDE 2.1.2 )
Severity: normal
Installed from:    SuSE
Compiler:          gcc version 2.95.2 19991024 (release)
OS:                Not Specified
OS/Compiler notes: Not Specified

When ever I start, 'kmix' is running.  I often kill it because it it
is constantly running and using about 2% of my CPU -- even if everything
else is idle.  This is wrong, especially on a laptop where this may be
contributing as much as a 5% extra drain on my battery for no good reason.

In doing a strace of it, you can see its doing some sort of busy looping
in the absence of any work to do rather than being event driven. (output
at end of note).

Note that the select timeout is approximately .196 seconds (196ms) followed by
10 calls to getimeofday at 4ms intervals, summing approximately .2 seconds.  
Every third .2 second interval, 16 ioctls are made to get status.  Here is
seems like it'd be real useful to ask the owner of the SOUND_MIXER device
for 1 ioctl that returns all of the information requested in 1 system call.

This averages to about 70 system calls per second.  Additionally, ltrace
reveals additionally approximately 1008 library calls per second.  I'd include
output, but it's *very* long.  

This is a large amount CPU burnt doing 'nothing'.  Given, for example, that
the system wait parameter before it calls the system power-idle is 300ms of
'idle', that means it will never get called.  It also means I'm losing
much system cache benefits/instruction prefetch when executing any other
CPU intensive operation.



select(8, [3 4 5 7], NULL, NULL, {0, 195592}) = 0 (Timeout)
gettimeofday({991319205, 970457}, NULL) = 0
gettimeofday({991319205, 970848}, NULL) = 0
gettimeofday({991319205, 971203}, NULL) = 0
gettimeofday({991319205, 971557}, NULL) = 0
gettimeofday({991319205, 971912}, NULL) = 0
gettimeofday({991319205, 972266}, NULL) = 0
gettimeofday({991319205, 972621}, NULL) = 0
gettimeofday({991319205, 972975}, NULL) = 0
gettimeofday({991319205, 973328}, NULL) = 0
gettimeofday({991319205, 973682}, NULL) = 0
ioctl(4, FIONREAD, [0])                 = 0
gettimeofday({991319205, 974370}, NULL) = 0
select(8, [3 4 5 7], NULL, NULL, {0, 195665}) = 0 (Timeout)
gettimeofday({991319206, 170490}, NULL) = 0
gettimeofday({991319206, 170885}, NULL) = 0
gettimeofday({991319206, 171241}, NULL) = 0
gettimeofday({991319206, 171597}, NULL) = 0
gettimeofday({991319206, 171951}, NULL) = 0
gettimeofday({991319206, 172306}, NULL) = 0
gettimeofday({991319206, 172661}, NULL) = 0
gettimeofday({991319206, 173016}, NULL) = 0
gettimeofday({991319206, 173370}, NU.LL) = 0
gettimeofday({991319206, 173726}, NULL) = 0
ioctl(8, SOUND_MIXER_READ_VOLUME, 0xbfffecb0) = 0
ioctl(8, SOUND_MIXER_READ_RECSRC, 0xbfffecb0) = 0
ioctl(8, SOUND_MIXER_READ_PCM, 0xbfffecb0) = 0
ioctl(8, SOUND_MIXER_READ_RECSRC, 0xbfffecb0) = 0
ioctl(8, SOUND_MIXER_READ_SPEAKER, 0xbfffecb0) = 0
ioctl(8, SOUND_MIXER_READ_RECSRC, 0xbfffecb0) = 0
ioctl(8, SOUND_MIXER_READ_LINE, 0xbfffecb0) = 0
ioctl(8, SOUND_MIXER_READ_RECSRC, 0xbfffecb0) = 0
ioctl(8, SOUND_MIXER_READ_MIC, 0xbfffecb0) = 0
ioctl(8, SOUND_MIXER_READ_RECSRC, 0xbfffecb0) = 0
ioctl(8, SOUND_MIXER_READ_CD, 0xbfffecb0) = 0
ioctl(8, SOUND_MIXER_READ_RECSRC, 0xbfffecb0) = 0
ioctl(8, SOUND_MIXER_READ_IGAIN, 0xbfffecb0) = 0
ioctl(8, SOUND_MIXER_READ_RECSRC, 0xbfffecb0) = 0
ioctl(8, SOUND_MIXER_READ_LINE1, 0xbfffecb0) = 0
ioctl(8, SOUND_MIXER_READ_RECSRC, 0xbfffecb0) = 0
ioctl(8, 0x80044d16, 0xbfffecb0)        = 0
ioctl(8, SOUND_MIXER_READ_RECSRC, 0xbfffecb0) = 0
ioctl(4, FIONREAD, [0])                 = 0
gettimeofday({991319206, 198563}, NULL) = 0
select(8, [3 4 5 7], NULL, NULL, {0, 171472}) = 0 (Timeout)
gettimeofday({991319206, 370498}, NULL) = 0
gettimeofday({991319206, 370894}, NULL) = 0
gettimeofday({991319206, 371252}, NULL) = 0
gettimeofday({991319206, 371606}, NULL) = 0
gettimeofday({991319206, 371961}, NULL) = 0
gettimeofday({991319206, 372317}, NULL) = 0
gettimeofday({991319206, 372671}, NULL) = 0
gettimeofday({991319206, 373025}, NULL) = 0
gettimeofday({991319206, 373380}, NULL) = 0
gettimeofday({991319206, 373735}, NULL) = 0
ioctl(4, FIONREAD, [0])                 = 0
gettimeofday({991319206, 374424}, NULL) = 0
select(8, [3 4 5 7], NULL, NULL, {0, 195611}) = 0 (Timeout)
gettimeofday({991319206, 570486}, NULL) = 0
gettimeofday({991319206, 570924}, NULL) = 0
gettimeofday({991319206, 571286}, NULL) = 0
gettimeofday({991319206, 571645}, NULL) = 0
gettimeofday({991319206, 572004}, NULL) = 0
gettimeofday({991319206, 572363}, NULL) = 0
gettimeofday({991319206, 572723}, NULL) = 0
gettimeofday({991319206, 573082}, NULL) = 0
gettimeofday({991319206, 573439}, NULL) = 0
gettimeofday({991319206, 573796}, NULL) = 0
ioctl(4, FIONREAD, [0])                 = 0
gettimeofday({991319206, 574493}, NULL) = 0
select(8, [3 4 5 7], NULL, NULL, {0, 95718}) = 0 (Timeout)
gettimeofday({991319206, 670484}, NULL) = 0
ioctl(8, SOUND_MIXER_READ_VOLUME, 0xbfffecb0) = 0
ioctl(8, SOUND_MIXER_READ_RECSRC, 0xbfffecb0) = 0
ioctl(8, SOUND_MIXER_READ_PCM, 0xbfffecb0) = 0
ioctl(8, SOUND_MIXER_READ_RECSRC, 0xbfffecb0) = 0
ioctl(8, SOUND_MIXER_READ_SPEAKER, 0xbfffecb0) = 0
ioctl(8, SOUND_MIXER_READ_RECSRC, 0xbfffecb0) = 0
ioctl(8, SOUND_MIXER_READ_LINE, 0xbfffecb0) = 0
ioctl(8, SOUND_MIXER_READ_RECSRC, 0xbfffecb0) = 0
ioctl(8, SOUND_MIXER_READ_MIC, 0xbfffecb0) = 0
ioctl(8, SOUND_MIXER_READ_RECSRC, 0xbfffecb0) = 0
ioctl(8, SOUND_MIXER_READ_CD, 0xbfffecb0) = 0
ioctl(8, SOUND_MIXER_READ_RECSRC, 0xbfffecb0) = 0
ioctl(8, SOUND_MIXER_READ_IGAIN, 0xbfffecb0) = 0
ioctl(8, SOUND_MIXER_READ_RECSRC, 0xbfffecb0) = 0
ioctl(8, SOUND_MIXER_READ_LINE1, 0xbfffecb0) = 0
ioctl(8, SOUND_MIXER_READ_RECSRC, 0xbfffecb0) = 0
ioctl(8, 0x80044d16, 0xbfffecb0)        = 0
ioctl(8, SOUND_MIXER_READ_RECSRC, 0xbfffecb0) = 0
gettimeofday({991319206, 695033}, NULL) = 0
ioctl(4, FIONREAD, [0])                 = 0
gettimeofday({991319206, 695724}, NULL) = 0
select(8, [3 4 5 7], NULL, NULL, {0, 74311}) = 0 (Timeout)
gettimeofday({991319206, 770487}, NULL) = 0
gettimeofday({991319206, 770882}, NULL) = 0
gettimeofday({991319206, 771242}, NULL) = 0
gettimeofday({991319206, 771600}, NULL) = 0
gettimeofday({991319206, 771958}, NULL) = 0
gettimeofday({991319206, 772316}, NULL) = 0
gettimeofday({991319206, 772674}, NULL) = 0
gettimeofday({991319206, 773032}, NULL) = 0
gettimeofday({991319206, 773390}, NULL) = 0
gettimeofday({991319206, 773748}, NULL) = 0
ioctl(4, FIONREAD, [0])                 = 0
gettimeofday({991319206, 774494}, NULL) = 0


-- 
The above thoughts and           | They may have nothing to do with
writings are my own.             | the opinions of my employer. :-)
L A Walsh                        | Trust Technology, Core Linux, SGI
law@sgi.com                      | Voice: (650) 933-5338




(Submitted via bugs.kde.org)
(Called from KBugReport dialog. Fields OS manually changed)

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