Re: [PATCH v3 1/3] rcutorture: Allow a negative value for nfakewriters

Paul E. McKenney
2025-02-26T14:50:03Z

On Wed, Feb 26, 2025 at 03:29:09PM +0100, Uladzislau Rezki wrote:
> On Tue, Feb 25, 2025 at 04:24:09PM -0500, Joel Fernandes wrote:
> > On Tue, Feb 25, 2025 at 12:00:18PM +0100, Uladzislau Rezki (Sony) wrote:
> > > Currently "nfakewriters" parameter can be set to any value but
> > > there is no possibility to adjust it automatically based on how
> > > many CPUs a system has where a test is run on.
> > >
> > > To address this, if the "nfakewriters" is set to negative it will
> > > be adjusted to num_online_cpus() during torture initialization.
> > >
> > > Reviewed-by: Paul E. McKenney <paulmck@kernel.org>
> > > Signed-off-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
> > > ---
> > > kernel/rcu/rcutorture.c | 22 ++++++++++++++++------
> > > 1 file changed, 16 insertions(+), 6 deletions(-)
> > >
> > > diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c
> > > index d98b3bd6d91f..f376262532ce 100644
> > > --- a/kernel/rcu/rcutorture.c
> > > +++ b/kernel/rcu/rcutorture.c
> > > @@ -148,6 +148,7 @@ MODULE_PARM_DESC(torture_type, "Type of RCU to torture (rcu, srcu, ...)");
> >
> > IMO, this should also be updated to reflect the possibily to set it negative
> > and hence to number CPUs:
> >
> > torture_param(int, nfakewriters, 4, "Number of RCU fake writer threads");
> >
> You can set it to a negative as well as to number of CPUs or any other
> number.

Joel does have a good point, though. Could I interest one of you in
updating the Documentation/admin-guide/kernel-parameters.txt entry for
rcutorture.nfakewriters? The rcutorture.nreaders entry is a decent guide.

Thanx, Paul