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

Joel Fernandes
2025-02-26T17:49:46Z

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).

thanks,

- Joel