Re: How how latent should non-preemptive scheduling be?

Ingo Molnar wrote:
* Sitsofe Wheeler <sitsofe@xxxxxxxxx> wrote:

Any ideas why the issue would go away with a debug kernel though?

hm, that's weird indeed. You could try to trace the full battery readout itself, via a script like this:

cat /debug/tracing/trace > /dev/null # drain trace
cat /proc/acpi/whatever cat /debug/tracing/trace > trace.txt

You can even turn on stack backtrace tracing feature, via:

echo stacktrace > /debug/tracing/iter_ctrl

this adds extra trace entries that show the call path of every reschedule. [this attribute is default-disabled.]

(Something bad seems to be happening with my kernels as I have been finding strange problems like network-manager detecting the wifi as a wired interface unless I did a make clean on my kernel sources before compiling). The stalling issue seems to keep coming and going and is currently showing up in both debug and non debug kernels.

There are traces when looking at battery information on both AC (where the problem is never there) and battery (where the problem always is there) here:
http://sucs.org/~sits/test/eeepc-debug/20080929/trace-on-ac.txt.bz2
http://sucs.org/~sits/test/eeepc-debug/20080929/trace-on-battery.txt.bz2 (15Mbytes uncompressed)

I wasn't quite sure how to tell when a reschedule was done. I simply did a grep schedule on the file and most of it seemed reasonable. One part that caught my eye was the following:

speaker-test-3891 [000] 1392.751699: __switch_to <-schedule
<idle>-0 [000] 1392.752070: account_scheduler_latency <-enqueue_task_fair
<idle>-0 [000] 1392.752091: __switch_to <-schedule
cat-7717 [000] 1392.752092: del_timer <-schedule_timeout
cat-7717 [000] 1392.772263: account_scheduler_latency <-enqueue_task_fair
cat-7717 [000] 1392.773224: __tasklet_schedule <-kbd_event
cat-7717 [000] 1392.773225: schedule_console_callback <-kbd_event
cat-7717 [000] 1392.773225: schedule_work <-schedule_console_callback
cat-7717 [000] 1392.773226: queue_work <-schedule_work
cat-7717 [000] 1392.773232: account_scheduler_latency <-enqueue_task_fair
cat-7717 [000] 1392.773240: account_scheduler_latency <-enqueue_task_fair
cat-7717 [000] 1392.773251: schedule_delayed_work <-put_queue
cat-7717 [000] 1392.773251: queue_delayed_work <-schedule_delayed_work
cat-7717 [000] 1392.773258: schedule_console_callback <-kbd_event
cat-7717 [000] 1392.773258: schedule_work <-schedule_console_callback
cat-7717 [000] 1392.773259: queue_work <-schedule_work
cat-7717 [000] 1392.773267: schedule_console_callback <-kbd_event
cat-7717 [000] 1392.773268: schedule_work <-schedule_console_callback
cat-7717 [000] 1392.773268: queue_work <-schedule_work
cat-7717 [000] 1392.807931: account_scheduler_latency <-enqueue_task_fair
cat-7717 [000] 1392.839464: __tasklet_schedule <-ath5k_intr
cat-7717 [000] 1392.839506: account_scheduler_latency <-enqueue_task_fair
cat-7717 [000] 1392.941867: __tasklet_schedule <-ath5k_intr
cat-7717 [000] 1393.005963: __tasklet_schedule <-ath5k_intr
cat-7717 [000] 1393.033222: __switch_to <-schedule

Here a schedule seemingly doesn't happen for a few hundredths of a second...

--
Sitsofe | http://sucs.org/~sits/
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