Re: [Xenomai] I-Pipe Tracer and linux ftrace

[Jan Kiszka <jan.kiszka@siemens.com>]

On 2015-06-22 22:47, Antoine Durand wrote:
> Thank you,
> 
> I really better understand the differences between the two traces sources.
> Indeed I am more interrested in ftrace datas for the moment.
> 
> I use a x86_64 CPCI cpu board with linux-3.16.7 and
> xenomai-3.0-rc4 with I-Pipe tracer Options On

The first thing is to switch the I-pipe tracer off, at least during
runtime. You don't need that overhead if you do ftrace event tracing.
But I suspect the issue elsewhere.

> 
> My problem may comes from trace-cmd actually, because it uses nearly two
> cores full time during ftrace collect.
> I don't known what for ! I used it to be able to plot datas in kernelshark
> but its overhead is too much.
> 
> I will try with no external tools, (just /sys/kernel/debug/tracing/*
> controls).

I'm using trace-cmd without such problems. Can you share your .config?
Could you also try 3.14.44-x86-9 (that's where I ran ftrace recently).

> 
> I had to disable nmi (echo 0 > /proc/sys/kernel/nmi_watchdog) at boot to
> avoid hard Lockup kernel crash when system load is high (running dohell for
> exemple). I don't think it can be linked.

Shouldn't happen either. Maybe related, and the system is in a general
bad shape due to configuration or patch issues.

Jan

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