linux-kernel - Re: [patch 2/3] nohz: change signal tick dependency to wakeup CPUs of member tasks

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Date:   Fri, 12 Feb 2021 11:00:41 -0300
From:   Marcelo Tosatti <mtosatti@...hat.com>
To:     Frederic Weisbecker <frederic@...nel.org>
Cc:     Peter Zijlstra <peterz@...radead.org>, linux-kernel@...r.kernel.org
Subject: Re: [patch 2/3] nohz: change signal tick dependency to wakeup CPUs
 of member tasks

On Fri, Feb 12, 2021 at 01:25:21PM +0100, Frederic Weisbecker wrote:
> On Thu, Jan 28, 2021 at 05:21:36PM -0300, Marcelo Tosatti wrote:
> > Rather than waking up all nohz_full CPUs on the system, only wakeup 
> > the target CPUs of member threads of the signal.
> > 
> > Reduces interruptions to nohz_full CPUs.
> > 
> > Signed-off-by: Marcelo Tosatti <mtosatti@...hat.com>
> > 
> > Index: linux-2.6/kernel/time/tick-sched.c
> > ===================================================================
> > --- linux-2.6.orig/kernel/time/tick-sched.c
> > +++ linux-2.6/kernel/time/tick-sched.c
> > @@ -444,9 +444,20 @@ EXPORT_SYMBOL_GPL(tick_nohz_dep_clear_ta
> >   * Set a per-taskgroup tick dependency. Posix CPU timers need this in order to elapse
> >   * per process timers.
> >   */
> > -void tick_nohz_dep_set_signal(struct signal_struct *sig, enum tick_dep_bits
> > bit)
> 
> Why not keeping the signal struct as a parameter?
> 
> Thanks.

All callers use "struct signal_struct *sig = tsk->signal" as
signal parameter anyway...

Can change parameters to (task, signal, bit) if you prefer.