* Alexandre Montplaisir ([email protected]) wrote: > On 13-04-18 01:23 PM, Mathieu Desnoyers wrote: > > * Alexandre Montplaisir ([email protected]) wrote: > >> On 13-04-18 01:07 PM, Mathieu Desnoyers wrote: > >>> * Alexandre Montplaisir ([email protected]) wrote: > >>>> On 13-04-18 02:11 AM, Amit Margalit wrote: > >>>>> Hi, > >>>>> > >>>>> Thank for the quick response. Here is the missing data: > >>>>> > >>>>> UST > >>>>> 2.6.32.12-205 (I had to make a tiny patch to make it compile) > >>>>> MemTotal: 24628852 kB > >>>>> lttng-ust-2.1.2 > >>>>> lttng-tools-2.1.1 > >>>>> lttng-modules-2.1.1 > >>>>> babeltrace-1.1.0 > >>>>> userspace-rcu-0.7.6 > >>>>> > >>>>> Which patch for 4MB? > >>>> Hi, > >>>> > >>>> Not sure if it's specifically this one that Matthew was talking about, > >>>> but we have such a patch in the PPA packages. See: > >>>> http://bazaar.launchpad.net/~lttng/lttng-tools/packaging-daily/view/head:/patches/0002-Increase-default-subbuffer-size-to-4MB.patch > >>> First, it should be noted that lttng enable-channel allow overriding the > >>> subbuffer size. > >> True that. But the value needs to be a power of two (which is not > >> immediately obvious to new users). And if it's not exactly a power of > >> two, it gets rejected, instead of simply rounding to the closest one. We > >> have a patch for that too. ;) > > I've never seen it on lttng-dev. Please share it, don't be shy :) > > Granted, it wasn't on lttng-dev. But an initial version was posted on > Redmine at: > https://bugs.lttng.org/issues/228
Yep, and I thoroughly reviewed it, and no new version has been sent since then. > > > > >>> It should be noted that lttng-modules 2.2 is going to output even _more_ > >>> events, so I don't think just making the buffers larger by default is > >>> the right approach. > >> If it's gonna output more events, don't we want larger sizes? > > No, because at some point, you want the default to take into account > > typical HW configuration limitations. Usually, systems should not be > > expected to be dedicated to tracing: whatever memory the tracer reserves > > is less memory available for page cache and application, and therefore > > more impact on the system. > > I think 4 MB isn't anywhere close to hardware limitations (at least for > desktop users, which are the main audience of the Ubuntu PPA packages). 4 MB * nr cpus * nr processes traced can be closer to HW limitations, even of desktops. Thanks, Mathieu > > > Cheers, > Alex > > >>> I think we need to port the "loglevel" from UST to lttng-modules ASAP, > >>> and assign a "debug" loglevel to events we don't care about by default. > >> This sounds like a good idea. > >> > >> My main concern was that most users don't read the man pages, don't > >> fiddle with custom flags, etc. They just run enable-event -a, then start > >> tracing. In this setup, they should not expect dropped events. > > Yep. Having loglevels should take care of that: debug-level events would > > not be enabled unless a specific loglevel is specified. > > > > Thanks, > > > > Mathieu > > > >> Cheers, > >> Alex > >> > >>> Thoughts ? > >>> > >>> Thanks, > >>> > >>> Mathieu > >>> > >>>>> Thanks, > >>>>> > >>>>> Amit Margalit > >>>>> IBM XIV - Storage Reinvented > >>>>> XIV-NAS Development Team > >>>>> Tel. 03-689-7774 > >>>>> Fax. 03-689-7230 > >>>>> > >>>>> > >>>>> > >>>>> From: Matthew Khouzam <[email protected]> > >>>>> To: <[email protected]> > >>>>> Date: 04/15/2013 05:24 PM > >>>>> Subject: Re: [lttng-dev] Limitations on subbuf_size / num_subbuf? > >>>>> > >>>>> > >>>>> > >>>>> Not at all a n00b question, but could you give some more info? what is > >>>>> your version of LTTng tools, are you using UST or kernel tracing? How > >>>>> much > >>>>> ram is on your system? Kernel version? > >>>>> > >>>>> I actually have the patched lttng that has standard subbuffer sizes of > >>>>> 4 > >>>>> mb, so I have not personnaly seen that problem. But the first thing I > >>>>> would do is upgrade to the latest stable. > >>>>> > >>>>> On 13-04-14 06:49 AM, Amit Margalit wrote: > >>>>> Hello, > >>>>> > >>>>> Sorry for the noob question. I seem to be unable to define the total of > >>>>> subbuf_size * num_subbuf higher than 4MB. I am getting ~30% discarded > >>>>> tracepoint data. > >>>>> > >>>>> Any assistance would be greatly appreciated. > >>>>> > >>>>> Amit Margalit > >>>>> IBM XIV - Storage Reinvented > >>>>> XIV-NAS Development Team > >>>>> Tel. 03-689-7774 > >>>>> Fax. 03-689-7230 > >>>> _______________________________________________ > >>>> lttng-dev mailing list > >>>> [email protected] > >>>> http://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev > -- Mathieu Desnoyers EfficiOS Inc. http://www.efficios.com _______________________________________________ lttng-dev mailing list [email protected] http://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev
