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 > >>> 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). 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 _______________________________________________ lttng-dev mailing list [email protected] http://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev
