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

Paul E. McKenney
2025-02-26T18:04:36Z

On Wed, Feb 26, 2025 at 12:49:41PM -0500, Joel Fernandes wrote:
>
>
> On 2/26/2025 9:29 AM, 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.
> Sorry I just meant amend the description to something like "Number of RCU fake
> writer threads (or set to -1 for NR_CPUs)", so user does not have to read code
> to know that (and update the kernel cmdline params document as well).

Should we also adjust the string for nreaders?

Thanx, Paul