[lttng-dev] About Lttng trace mode

[Thibault, Daniel]

Date: Mon, 3 Feb 2014 16:03:14 +0000 (UTC)
From: Mathieu Desnoyers <mathieu.desnoyers at efficios.com>

>----- Original Message -----
>> From: "Daniel Thibault" <Daniel.Thibault at drdc-rddc.gc.ca>
>> Sent: Thursday, November 14, 2013 12:01:25 PM
>> 
>>  [...]
>>    or by the consumer.  In discard mode, while a sub-buffer is locked for
>>    consumer access, should the writers go around the set of sub-buffers and
>>  [...]
>
>The paragraph above is true, except for the part "while a sub-buffer is locked for consumer access". In discard mode, as soon as the writer is filling up all sub-buffers, and thus the >produced sub-buffers count reaches the consumed sub-buffer count minus the number of sub-buffers in the buffer (this is a buffer full situation), events are discarded. This is done >independently of whether or not the consumer is currently locking a sub-buffer for reading.

   Good, subtle point.  The sub-buffer is marked for consumption ("read-ready"), just not actively locked ("being read").

Daniel U. Thibault
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