Comment 5 for bug 579117

Ok, so I installed latencytop and ran it. I've been looking at the
display but can't see anything specifically related to wireless
operation.

I started up rhythmbox and ran it, waiting for an underrun. When I got
one, I waited a few seconds and then hit refresh on the latencytop
display, then freeze.

On the left hand side under Global I see

events/1 194.3
kondemand/0 167.5
kondemand/1 102.4
jbd2/sda1-8 57.9
compiz 39.8
events/0 33.1
sundaemon 22.1
Xorg 18.1

everything else is below 10.0 ms.

Looking under events/1, I see that the cause is Scheduler: waiting for
CPU. Same for the two kondemand's. The jdb2/sda1-8 is doing three
things: writing buffer to disk (synchronous) which takes 57.9 ms,
Scheduler: waiting for cpu which is 2.1 ms, and writing a page to disk
which is 0.7 ms.

Well, none of that speaks to me, so I've un-frozen latencytop and now
I'm watching it refresh itself every 30s.

Generally under global I see that the scheduler: waiting for cpu is at
the top. I just saw an underrun in the log now I'm waiting for a
refresh.

Under global there is:

Scheduler: waiting for cpu 274.5 ms
Waiting for TTY data 268.0 ms
opening cdrom device 6.8 ms

everything else well below 10ms.

There is a waiting for event (poll) at 5.0ms that is 36.1%. Is that
meaningful?

The backtrace for that is
poll_schedule_timeout
do_poll
do_sys_poll
sys_poll
syscall_call

When I go back down into the detailed targets under Global, I can't find
any big percentage used up by any one of the targets.

I'm a bit stuck here, any more specific advice? Please and thanks!

On Sun, 2010-05-16 at 11:25 +0000, David Henningsson wrote:

> Good question. Perhaps you can verify that the wireless actually blocks
> everything for a long while, by running latencytop (install the
> latencytop package) and see if you get something that confirms the
> suspicion?
>
>
> ** Summary changed:
>
> - [USB-Audio - USB Audio CODEC ] Playback problem
> + Wireless blocks USB-Audio, leading to dropouts
>
> ** Package changed: alsa-driver (Ubuntu) => linux (Ubuntu)
>
> ** Changed in: linux (Ubuntu)
> Importance: Undecided => Medium
>

--
Regards,

Chris Hermansen · mailto:<email address hidden>