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Message #09317
[Bug 1219871] Re: when idle with screen blank, unity8 generates hundreds of context switches per second
As Qt switched from v8 to v4 (replacing the code that triggered this)
and we haven't seen this in a long time, we can close this now.
** Changed in: unity8 (Ubuntu)
Status: Confirmed => Incomplete
** Changed in: unity8 (Ubuntu)
Status: Incomplete => Invalid
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https://bugs.launchpad.net/bugs/1219871
Title:
when idle with screen blank, unity8 generates hundreds of context
switches per second
Status in “unity8” package in Ubuntu:
Invalid
Bug description:
To reproduce (on maguro, Samsung Galaxy Nexus):
sudo apt-get install sysstat
ensure idle has occurred and screen is now blank, ssh in and run
pidstat -w 10 1
Linux 3.0.0-3-maguro (ubuntu-phablet) 09/02/2013 _armv7l_
(2 CPU)
03:04:13 PM UID PID cswch/s nvcswch/s Command
03:04:23 PM 0 3 1.19 0.00 ksoftirqd/0
03:04:23 PM 0 9 1.29 0.00 ksoftirqd/1
03:04:23 PM 0 13 0.20 0.00 sync_supers
03:04:23 PM 0 20 21.99 0.00 kworker/0:1
03:04:23 PM 0 23 0.40 0.00 kinteractiveup
03:04:23 PM 0 69 1.29 0.00 kworker/1:1
03:04:23 PM 0 88 2.09 0.00 mmcqd/0
03:04:23 PM 0 96 0.30 0.00 dhd_watchdog
03:04:23 PM 0 97 8.46 0.00 dhd_dpc
03:04:23 PM 0 156 0.90 0.00 jbd2/mmcblk0p12
03:04:23 PM 103 418 0.50 0.00 dbus-daemon
03:04:23 PM 0 429 0.20 0.00 flush-179:0
03:04:23 PM 1000 493 70.05 0.00 surfaceflinger
03:04:23 PM 32011 613 0.20 0.00 init
03:04:23 PM 32011 658 0.10 0.00 dbus-daemon
03:04:23 PM 32011 713 467.86 0.10 unity8
03:04:23 PM 32011 788 0.10 0.00 upstart-dbus-br
03:04:23 PM 32011 790 0.10 0.00 upstart-dbus-br
03:04:23 PM 0 862 3.98 2.79 NetworkManager
03:04:23 PM 0 1179 0.10 0.00 wpa_supplicant
03:04:23 PM 32011 1219 0.10 0.40 indicator-netwo
03:04:23 PM 0 1237 0.20 0.00 ofonod
03:04:23 PM 32011 1335 0.10 0.00 mission-control
03:04:23 PM 32011 1339 0.40 0.00 telepathy-ofono
03:04:23 PM 0 1929 222.59 1.09 kworker/u:0
03:04:23 PM 0 2379 222.89 0.00 kworker/u:1
03:04:23 PM 32011 2944 0.10 2.19 pidstat
unity8 with PID 713 is performing ~450-470 context switches a second.
But what is it doing?
sudo add-apt-repository ppa:colin-king/white && sudo apt-get update && sudo apt-get install health-check
sudo health-check -p 713 -d 10
CPU usage:
PID Process USR% SYS% TOTAL%
713 unity8 27.29 6.40 33.69 (medium load)
^^ that's kinda busy!
Wakeups:
No wakeups detected
File I/O operations:
No file I/O operations detected
System calls traced:
PID Process Syscall Count Rate/Sec
713 unity8 futex 3904 390.2976
713 unity8 clock_gettime 1384 138.3637
713 unity8 poll 791 79.0792
713 unity8 read 789 78.8793
713 unity8 recvmsg 4 0.3999
713 unity8 write 4 0.3999
713 unity8 restart_syscall 1 0.1000
Total 6877 687.5196
Looks like it may be context switching like mad on a futex.
When the screen is not blank but device is idle, unity8 is far less busy.
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