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

Uladzislau Rezki
2025-02-26T15:40:13Z

On Wed, Feb 26, 2025 at 06:50:02AM -0800, Paul E. McKenney wrote:
> 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.
>
OK. Then i misunderstood Joel. It was about updating a documentation
about this!

Good point :)

--
Uladzislau Rezki