Re: events/0 thread in kernels 2.6.22*fc6 causing scheduling latency
On 8/27/07, Mike Fleetwood <mike.fleetwood(a)googlemail.com> wrote:
Hi,
Since I upgraded my FC6 box from kernel-2.6.20-1.2962.fc6 to
kernel-2.6.22.1-32.fc6, and now 2.6.22.2-42.fc6, I am getting pauses
from the whole OS. They last ~1 second and occur every few minutes.
Every application becomes unresponsive for the duration. The 1 second
scheduler latency this causes is long enough for my music player to be
effected and the audio track to be interrupted. This makes the fault
very easy to hear. At the same time kernel thread events/0 seems to
use all the CPU time. Here is the first few lines of top's output
when a pause happens:
top - 21:39:41 up 1:17, 2 users, load average: 1.05, 1.20, 1.24
Tasks: 138 total, 4 running, 134 sleeping, 0 stopped, 0 zombie
Cpu(s): 2.3%us, 29.3%sy, 68.4%ni, 0.0%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st
Mem: 2074880k total, 1355244k used, 719636k free, 62144k buffers
Swap: 1004052k total, 0k used, 1004052k free, 882684k cached
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
5525 mike 39 19 202m 81m 4016 R 68.4 4.0 13:07.46 hadcm3transum_5
6 root 15 -5 0 0 0 S 28.5 0.0 0:53.40 events/0
3619 mike 20 0 45620 8264 5856 S 0.9 0.4 0:18.58 xmms
3318 root 20 0 328m 46m 8132 S 0.6 2.3 1:39.60 Xorg
3524 mike 20 0 76728 23m 9640 S 0.6 1.2 1:13.15 bittorrent
3557 mike 20 0 211m 115m 30m S 0.6 5.7 3:54.24 firefox-bin
3489 mike 20 0 57240 23m 15m S 0.3 1.1 0:04.02 gnome-terminal
5583 root 20 0 2204 1100 832 R 0.3 0.1 0:01.14 top
28.5% CPU time used by events/0 of a single 3 second top refresh is
0.85 seconds of CPU time. Rebooting back to kernel 2.6.20 completely
fixes it.
Has any one else seen this issue?
Does anyone know what kernel thread events/0 does?
It's a per processor work queue. This is a data structure used to
handle deferred work. As you have only one processor, you get an
events/0 (events/1, etc.. in SMP).
I've never seen that thread taking so much cpu time... maybe a kernel
developer can throw some light here
Could this be related to CFS newly introduced into Fedora's
kernel 2.6.22?
Can anybody suggest how to fix this issue?
Thanks,
Mike
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