linux-kernel - Re: [PATCH] tracing: Use task_nice() in function __update_max

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Message-ID: <20140122230029.638e9a53@gandalf.local.home>
Date:	Wed, 22 Jan 2014 23:00:29 -0500
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	Dongsheng Yang <yangds.fnst@...fujitsu.com>,
	linux-kernel@...r.kernel.org, fweisbec@...il.com, mingo@...hat.com,
	Peter Zijlstra <peterz@...radead.org>
Subject: Re: [PATCH] tracing: Use task_nice() in function __update_max_tr()
 to get the nice value of task.

On Wed, 22 Jan 2014 22:56:32 -0500
Steven Rostedt <rostedt@...dmis.org> wrote:

> On Wed, 22 Jan 2014 17:41:45 -0500
> Dongsheng Yang <yangds.fnst@...fujitsu.com> wrote:
> 
> > There is already a function named task_nice in sched.h to get the nice value
> > of task_struct. We can use it in __update_max_tr() rather than calculate it
> > manually.
> > 
> > Signed-off-by: Dongsheng Yang <yangds.fnst@...fujitsu.com>
> > ---
> >  kernel/trace/trace.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
> > index 9d20cd9..ec149b4 100644
> > --- a/kernel/trace/trace.c
> > +++ b/kernel/trace/trace.c
> > @@ -970,7 +970,7 @@ __update_max_tr(struct trace_array *tr, struct task_struct *tsk, int cpu)
> >  	else
> >  		max_data->uid = task_uid(tsk);
> >  
> > -	max_data->nice = tsk->static_prio - 20 - MAX_RT_PRIO;
> > +	max_data->nice = task_nice(tsk);
> 
> Except that's a function call in a critical path. Switch it to
> TASK_NICE(), and I'll take the patch.

Bah, I just noticed that TASK_NICE is in kernel/sched/sched.h not
include/linux/sched.h

Peter, is there a reason that task_nice() is not a static inline in
sched.h and have these macros there too? They only reference fields in
task_struct that are already defined there. I don't see why they need
to be private to kernel/sched.

-- Steve

> 
> Thanks,
> 
> -- Steve
> 
> >  	max_data->policy = tsk->policy;
> >  	max_data->rt_priority = tsk->rt_priority;
> >  
> 

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