Re: [Xen-devel] [PATCH v6 4/5] xen: add per-cpu buffer option to debugtrace

[Jan Beulich <jbeulich@xxxxxxxx>]

On 09.09.2019 09:59, Jan Beulich wrote:
> On 09.09.2019 09:35, Juergen Gross wrote:
>> debugtrace is normally writing trace entries into a single trace
>> buffer. There are cases where this is not optimal, e.g. when hunting
>> a bug which requires writing lots of trace entries and one cpu is
>> stuck. This will result in other cpus filling the trace buffer and
>> finally overwriting the interesting trace entries of the hanging cpu.
>>
>> In order to be able to debug such situations add the capability to use
>> per-cpu trace buffers. This can be selected by specifying the
>> debugtrace boot parameter with the modifier "cpu:", like:
>>
>>   debugtrace=cpu:16
>>
>> At the same time switch the parsing function to accept size modifiers
>> (e.g. 4M or 1G).
>>
>> Printing out the trace entries is done for each buffer in order to
>> minimize the effort needed during printing. As each entry is prefixed
>> with its sequence number sorting the entries can easily be done when
>> analyzing them.
>>
>> Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
> 
> Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>

Oh, no - I have to take this back. Looking at patch 5 I notice
that you now only ever write last_cpu; you must have lost its
consumer.

Jan

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