Messages in this thread | | | Date | Wed, 13 May 2015 10:23:38 -0700 | From | "Paul E. McKenney" <> | Subject | Re: [PATCH tip/core/rcu 04/13] rcutorture: Allow negative values of nreaders to oversubscribe |
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On Tue, May 12, 2015 at 06:03:13PM -0700, josh@joshtriplett.org wrote: > On Tue, May 12, 2015 at 03:58:04PM -0700, Paul E. McKenney wrote: > > From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> > > > > By default, with rcutorture.nreaders equal to -1, rcutorture provisions > > N-1 reader kthreads, where N is the number of CPUs. This avoids > > rcutorture-induced stalls, but also avoids heavier levels of torture. > > This commit therefore allows negative values of rcutorture.nreaders > > to specify larger numbers of reader kthreads, so that for example > > rcutorture.nreaders=-2 provisions N kthreads and rcutorture.nreaders=-5 > > provisions N+3 kthreads. > > > > Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> > > That seems rather excessively arcane. Then again, I guess we started > down the road to arcana when we allowed -1 to mean N-1.
Indeed...
> However, could you please document this in the module parameter > documentation?
Good point, fixed!
Thanx, Paul
> > kernel/rcu/rcutorture.c | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c > > index a67ef6ff86b0..7294d605c481 100644 > > --- a/kernel/rcu/rcutorture.c > > +++ b/kernel/rcu/rcutorture.c > > @@ -1701,7 +1701,7 @@ rcu_torture_init(void) > > if (nreaders >= 0) { > > nrealreaders = nreaders; > > } else { > > - nrealreaders = num_online_cpus() - 1; > > + nrealreaders = num_online_cpus() - 2 - nreaders; > > if (nrealreaders <= 0) > > nrealreaders = 1; > > } > > -- > > 1.8.1.5 > > >
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