[ovs-dev] [PATCH 3/3] poll-loop: Log backtraces when CPU usage is high.

Ethan Jackson ethan at nicira.com
Thu Oct 25 17:11:52 UTC 2012


Good idea, I've folded that in.

Ethan

On Wed, Oct 24, 2012 at 6:58 PM, Ben Pfaff <blp at nicira.com> wrote:
> On Wed, Oct 24, 2012 at 01:49:09PM -0700, Ethan Jackson wrote:
>> Often when debugging Open vSwitch, one will see in the logs that
>> CPU usage has been high for some period of time, but it's totally
>> unclear why.  In an attempt to remedy the situation, this patch
>> logs backtraces taken at regular intervals as a poor man's
>> profiling alternative.
>>
>> Signed-off-by: Ethan Jackson <ethan at nicira.com>
>
> I only have a minor cosmetic suggestion.  Here:
>
>>      if (cpu_usage >= 0) {
>>          ds_put_format(&s, " (%d%% CPU usage)", cpu_usage);
>> +
>> +        if (!vlog_should_drop(THIS_MODULE, level, &trace_rl)) {
>> +            ds_put_cstr(&s, "\nBacktraces:\n");
>> +            format_backtraces(&s, 2);
>> +        }
>
> it might make sense to drop "Backtraces:\n" (you probably want to keep
> the newline) because otherwise if there aren't any repeated backtraces
> or if we're on a system without backtrace() then you'll get a
> funny-looking two-line log message without any additional detail.
>
> Otherwise I think (hope, anyway) that this will be very useful.



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