[lttng-dev] Limitations on subbuf_size / num_subbuf?

[Mathieu Desnoyers]

* Alexandre Montplaisir (alexmonthy at voxpopuli.im) 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.

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.

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.

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 <matthew.khouzam at ericsson.com>
> > To:     <lttng-dev at lists.lttng.org>
> > 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 
> 
> 
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-- 
Mathieu Desnoyers
EfficiOS Inc.
http://www.efficios.com