----- Original Message ----- > From: "Sébastien Barthélémy" <[email protected]> > To: [email protected] > Sent: Wednesday, April 16, 2014 12:22:42 PM > Subject: [lttng-dev] memory usage depending on number and size of subbuffers
> Hi all, > LTTng uses more memory than I expected. On the simple experiment below one > can see that the "cached" memory increases by > subbuf_size*num_cpu*(num_subbuf+1) > That's not a big deal, but I did not expect the "+1". > Does somebody know where it comes from? It is the extra sub-buffer needed for reading a sub-buffer while the other sub-buffers are written into. It's needed for snapshotting data while tracing is active. Thanks, Mathieu > -- Regards, Sebastien > 12M == 2M*2*(2+1) > 24M == 4M*2*(2+1) > 20M == 2M*2*(4+1) > 40M == 4M*2*(4+1) > # grep processor /proc/cpuinfo > processor : 0 > processor : 1 > # lttng create > Session auto-20140416-180246 created. > Traces will be written in /root/lttng-traces/auto-20140416-180246 > # free -m > total used free shared buffers cached > Mem: 1002 670 332 0 22 250 > -/+ buffers/cache: 397 605 > Swap: 0 0 0 > # lttng enable-channel channel0 --num-subbuf 2 --subbuf-size 2M -u > UST channel channel0 enabled for session auto-20140416-180246 > # free -m > total used free shared buffers cached > Mem: 1002 682 320 0 22 262 > -/+ buffers/cache: 397 605 > Swap: 0 0 0 > # lttng destroy > Session auto-20140416-180246 destroyed > # lttng create > Session auto-20140416-180317 created. > Traces will be written in /root/lttng-traces/auto-20140416-180317 > # free -m > total used free shared buffers cached > Mem: 1002 670 332 0 22 250 > -/+ buffers/cache: 397 605 > Swap: 0 0 0 > # lttng enable-channel channel0 --num-subbuf 2 --subbuf-size 4M -u > UST channel channel0 enabled for session auto-20140416-180317 > # free -m > total used free shared buffers cached > Mem: 1002 694 307 0 22 274 > -/+ buffers/cache: 397 605 > Swap: 0 0 0 > # lttng destroy > Session auto-20140416-180317 destroyed > # lttng create > Session auto-20140416-180339 created. > Traces will be written in /root/lttng-traces/auto-20140416-180339 > # free -m > total used free shared buffers cached > Mem: 1002 670 332 0 22 250 > -/+ buffers/cache: 397 605 > Swap: 0 0 0 > # lttng enable-channel channel0 --num-subbuf 4 --subbuf-size 2M -u > UST channel channel0 enabled for session auto-20140416-180339 > # free -m > total used free shared buffers cached > Mem: 1002 690 311 0 22 270 > -/+ buffers/cache: 397 605 > Swap: 0 0 0 > # lttng destroy > Session auto-20140416-180339 destroyed > # lttng create > Session auto-20140416-180406 created. > Traces will be written in /root/lttng-traces/auto-20140416-180406 > # free -m > total used free shared buffers cached > Mem: 1002 670 332 0 22 250 > -/+ buffers/cache: 397 605 > Swap: 0 0 0 > # lttng enable-channel channel0 --num-subbuf 4 --subbuf-size 4M -u > UST channel channel0 enabled for session auto-20140416-180406 > # free -m > total used free shared buffers cached > Mem: 1002 710 292 0 22 290 > -/+ buffers/cache: 397 605 > _______________________________________________ > lttng-dev mailing list > [email protected] > http://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev -- Mathieu Desnoyers EfficiOS Inc. http://www.efficios.com
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