[lttng-dev] lttng create --output problem

[Mathieu Desnoyers]

* Ryan.Kyser at jci.com (Ryan.Kyser at jci.com) wrote:
> Mathieu:
> 
> Looks good! I went through my menuconfig and enabled all of these.
> 
> One suggestion -- change 'requied' to 'required' in the line 'Kernel 
> config options requied'

Done. Thanks !

Mathieu

> 
> Thank you,
> 
> Ryan Kyser
> 
> 
> 
> 
> From:
> Mathieu Desnoyers <mathieu.desnoyers at efficios.com>
> To:
> Ryan.Kyser at jci.com
> Cc:
> lttng-dev at lists.lttng.org, David Goulet <dgoulet at efficios.com>
> Date:
> 04/06/2012 12:31 PM
> Subject:
> Re: [lttng-dev] lttng create --output problem
> 
> 
> 
> * Mathieu Desnoyers (mathieu.desnoyers at efficios.com) wrote:
> > * Ryan.Kyser at jci.com (Ryan.Kyser at jci.com) wrote:
> > > *** I'm resending this because I saw that mailman scrubbed my 
> message.***
> > > 
> > > 
> > > Mathieu:
> > > 
> > > I have provided the requested information below.
> > > 
> > > Also, I want to include some additional information which may (or may 
> not) 
> > > be part of the problem. When lttng-sessiond starts, I'm met with a 
> > > modprobe error (see below). It looks as if this module is not being 
> built 
> > > at compile time because CONFIG_KVM is not enabled. However, if I go 
> into 
> > > the kernel menuconfig and search for KVM, no results are returned.
> > 
> > Normally lttng-modules should use the features that are there without
> > complaining too much.
> > 
> > What I notice is that you don't have CONFIG_HAVE_SYSCALL_TRACEPOINTS
> > enabled. So -k -a is enabling both tracepoints and syscalls, and given
> > that syscall enabling returns ENOSYS, it prints this error and bails
> > out.
> > 
> > The correct behavior would be to only fail of _both_ tracepoint and
> > syscall instrumentation fail to enable.
> > 
> > Short term solution for you would be to enable
> > CONFIG_HAVE_SYSCALL_TRACEPOINTS in your kernel.
> 
> FYI, here is the update. Feedback is welcome,
> 
> commit d0a5ff7d8479de94f1082055d1d940d660027fc8
> Author: Mathieu Desnoyers <mathieu.desnoyers at efficios.com>
> Date:   Fri Apr 6 12:32:22 2012 -0400
> 
>     Fix: document required and optional kernel config options in README
>  
>     Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers at efficios.com>
> 
> diff --git a/README b/README
> index abbfd27..ac0dc88 100644
> --- a/README
> +++ b/README
> @@ -1,7 +1,7 @@
>  LTTng 2.0 modules
>  
>  Mathieu Desnoyers
> -February 8, 2012
> +April 6, 2012
>  
>  LTTng 2.0 kernel modules build against a vanilla or distribution kernel, 
> without
>  need for additional patches. Other features:
> @@ -48,9 +48,42 @@ LTTng 0.x patchset, but the lttng-modules 2.0 replace 
> the lttng-modules
>  0.x, so both tracers cannot be installed at the same time for a given
>  kernel version.
>  
> -LTTng-modules depends on having kallsyms enabled in the kernel it is
> -built against. Ideally, if you want to have system call tracing, the
> -"Trace Syscalls" feature should be enabled too. 
> +
> +* Kernel config options requied
> +
> +CONFIG_KALLSYMS: required
> +  * See wrapper/ files. This is necessary until the few required missing
> +    symbols are exported to GPL modules from mainline.
> +CONFIG_HIGH_RES_TIMERS: required
> +  * Needed for LTTng 2.0 clock source.
> +CONFIG_TRACEPOINTS: required
> +    kernel tracepoint instrumentation
> +    * Enabled as side-effect of any of the perf/ftrace/blktrace
> +      instrumentation features.
> +
> +
> +* Kernel config options supported (optional)
> +
> +The following kernel configuration options will affect the features
> +available from LTTng:
> +
> +
> +CONFIG_HAVE_SYSCALL_TRACEPOINTS:
> +            system call tracing
> +               lttng enable-event -k --syscall
> +               lttng enable-event -k -a
> +CONFIG_PERF_EVENTS:
> +            performance counters
> +               lttng add-context -t perf:*
> +CONFIG_EVENT_TRACING:
> +            needed to allow block layer tracing
> +CONFIG_KPROBES: 
> +            Dynamic probe.
> +               lttng enable-event -k --probe ...
> +CONFIG_KRETPROBES:
> +            Dynamic function entry/return probe.
> +               lttng enable-event -k --function ...
> +
>  
>  * Note about Perf PMU counters support
>  
> 
> -- 
> Mathieu Desnoyers
> Operating System Efficiency R&D Consultant
> EfficiOS Inc.
> http://www.efficios.com
> 
> 
> 

-- 
Mathieu Desnoyers
Operating System Efficiency R&D Consultant
EfficiOS Inc.
http://www.efficios.com