---------------------------------------------------------------------- Date: Mon, 5 May 2014 08:24:39 +0000 From: "Sadon, Mirit" <[email protected]> Cc: "Eshel, Ayelet" <[email protected]>
> I am working with the lttng trace to see how it affects are program > performance, > But if I don't limit the size of the trace file collected it fills all the > space in the partition I specify. > What does it mean if I start the trace and limit the trace file to let say > 1GB. > Would the trace stop after it reaches the limit or it will continue and > override the previous collected points? > > I tried by using this command when creating the channel but it didn't work. > > lttng enable-channel perf --subbuf-size 262144 -C 262144 -W 32 --num-subbuf > 32 -u > > We are working with lttng version 2.04. > > Mirit Sadon > EMC2 This feature may not have been mature with version 2.0.4; I would recommend upgrading to at least 2.3 if not 2.4. Your command sets up a single user-space channel named perf which uses a 32-part buffer of total size 32*262144=8388608 (8 MiB). The trace is itself limited to 32 chunks of size 262144 each. By default, user-space channels run in discard mode. So in this case LTTng should capture about 8 MiB of events to disc, and a further 8 MiB in memory before "giving up" altogether. When the trace is started the 8 MiB buffer will start filling up, and the consumer daemon will start dumping the events to the trace file. Once the trace file saturates at 8 MiB total size, the consumer daemon will stop emptying the buffer. The buffer will then capture another 8 MiB of events. Once the buffer is full, LTTng will systematically discard new events as they occur. It would be an interesting feature if the snapshot command could be used at this point to dump the 8 MiB of otherwise-lost events to another trace file. Daniel U. Thibault Protection des systèmes et contremesures (PSC) | Systems Protection & Countermeasures (SPC) Cyber sécurité pour les missions essentielles (CME) | Mission Critical Cyber Security (MCCS) R & D pour la défense Canada - Valcartier (RDDC Valcartier) | Defence R&D Canada - Valcartier (DRDC Valcartier) 2459 route de la Bravoure Québec QC G3J 1X5 CANADA Vox : (418) 844-4000 x4245 Fax : (418) 844-4538 NAC : 918V QSDJ <http://www.travelgis.com/map.asp?addr=918V%20QSDJ> Gouvernement du Canada | Government of Canada <http://www.valcartier.drdc-rddc.gc.ca/> _______________________________________________ lttng-dev mailing list [email protected] http://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev
