[lttng-dev] "No space left on device" results in corrupt trace data set

[Woegerer, Paul]

On 11/16/2012 04:54 PM, Julien Desfossez wrote:
> On 16/11/12 10:39 AM, Woegerer, Paul wrote:
>> Does that mean that the live tracing feature that currently lives in the
>> lttngtop-live branch will go into lttng-tools and babeltrace any time soon ?
> 
> The main change of lttng-tools 2.2 is the live tracing feature.
> The way it is implemented in the lttngtop-live branch is more a
> proof-of-concept, we will be starting the clean implementation
> discussions here as soon as we have lttng-tools 2.1 released (which
> should be around the end of this month).
> 
> In the mean time, to solve the problem you are currently experiencing,
> you could manually add a flush on the metadata channel after the session
> is started to make sure it is written on disk quickly (that's what is
> done in lttngtop-live at the beginning). Of course like David said, if

I will try that. Thanks !

--
Paul

> you have new events/applications enabled during tracing, the metadata
> needs to be flushed again.
> 
> Thanks,
> 
> Julien
> 
> 
>>
>> Thanks
>> Paul
>>
>>>
>>> Thanks,
>>>
>>> Mathieu
>>>
>>>>
>>>> Cheers!
>>>> David
>>>>
>>>> Woegerer, Paul:
>>>>> Hi,
>>>>>
>>>>> embedded users sometimes have to trace to tmpfs (e.g. streaming in not
>>>>> an option due to missing network connectivity).
>>>>>
>>>>> Ramdisks of 16M to 128M size are created and as long as the ram disk
>>>>> does not get full, tracing works fine. Unfortunately if the disk gets
>>>>> full things fall apart:
>>>>>
>>>>> PERROR: Error in file write: No space left on device [in
>>>>> lttng_consumer_on_read_subbuffer_mmap() at consumer.c:1367]
>>>>>
>>>>> The consumer daemon will not be able to write the metadata channel and
>>>>> therefore the trace data set will be unusable (cannot be read with
>>>>> babeltrace).
>>>>>
>>>>> -rwxrwxrwx 1 testuser users        0 Nov 16 11:22 metadata
>>>>> -rwxrwxrwx 1 testuser users 15728640 Nov 16 11:22 myevents_0
>>>>> -rwxrwxrwx 1 testuser users     4096 Nov 16 11:22 myevents_1
>>>>>
>>>>> Is it possible to somehow reserve the file size (fallocate) for metadata
>>>>> so that in case the disk gets full at least the metadata gets written
>>>>> and the resulting trace set is readable with babeltrace ?
>>>>>
>>>>> I wonder if that is possible at all. The consumer daemon doesn't know
>>>>> upfront how much would need to be reserved for metadata, right ?
>>>>>
>>>>> Any ideas ?
>>>>>
>>>>> Thanks,
>>>>> Paul
>>>>>
>>>>>
>>>>
>>>> _______________________________________________
>>>> lttng-dev mailing list
>>>> lttng-dev at lists.lttng.org
>>>> http://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev
>>>
>>
>>


-- 
Paul Woegerer | SW Development Engineer
http://go.mentor.com/sourceryanalyzer

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