[Devel] Re: [PATCH 3/3] ftrace: add ability to only trace swapper tasks

Ingo Molnar mingo at elte.hu
Thu Dec 4 00:06:29 PST 2008


* Steven Rostedt <rostedt at goodmis.org> wrote:

> From: Steven Rostedt <srostedt at redhat.com>
> 
> Impact: New feature
> 
> This patch lets the swapper tasks of all CPUS be filtered by the
> set_ftrace_pid file.
> 
> If '0' is echoed into this file, then all the idle tasks (aka swapper)
> is flagged to be traced.  This affects all CPU idle tasks.
> 
> Signed-off-by: Steven Rostedt <srostedt at redhat.com>
> ---
>  kernel/trace/ftrace.c |   74 +++++++++++++++++++++++++++++++++++++++++-------
>  1 files changed, 63 insertions(+), 11 deletions(-)

okay, i've applied it - but i dont like the extra complexity of +50 lines 
at all.

This is an area where the 'PID namespaces via struct pid pointers' model 
breaks down and forces collateral complexity into other subsystems, and 
where a simple integer based filter is so intuitive.

Eric, can you see any way to simplify this? It looks horrible.

	Ingo
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