Commit-ID: 3838cc1850ccd09f93e729e9047ec1995026f83e
Gitweb: http://git.kernel.org/tip/3838cc1850ccd09f93e729e9047ec1995026f83e
Author: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
AuthorDate: Thu, 12 Mar 2015 13:55:48 -0700
Committer: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
CommitDate: Wed, 27 May 2015 12:59:57 -0700
rcutorture: Allow negative values of nreaders to oversubscribe
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@xxxxxxxxxxxxxxxxxx>
[ paulmck: Update documentation, as suggested by Josh Triplett. ]
---
Documentation/kernel-parameters.txt | 6 +++++-
kernel/rcu/rcutorture.c | 2 +-
2 files changed, 6 insertions(+), 2 deletions(-)
diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 61ab162..04b8110 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -3101,7 +3101,11 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
test, hence the "fake".
rcutorture.nreaders= [KNL]
- Set number of RCU readers.
+ Set number of RCU readers. The value -1 selects
+ N-1, where N is the number of CPUs. A value
+ "n" less than -1 selects N-n-2, where N is again
+ the number of CPUs. For example, -2 selects N
+ (the number of CPUs), -3 selects N+1, and so on.
rcutorture.object_debug= [KNL]
Enable debug-object double-call_rcu() testing.
diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c
index a67ef6f..7294d60 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;
}
--
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