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| author | Paul E. McKenney <paulmck@linux.vnet.ibm.com> | 2015-03-12 13:55:48 -0700 |
|---|---|---|
| committer | Paul E. McKenney <paulmck@linux.vnet.ibm.com> | 2015-05-27 12:59:57 -0700 |
| commit | 3838cc1850ccd09f93e729e9047ec1995026f83e (patch) | |
| tree | 10c704c147266b9083bc0f9a16e51116847057f4 | |
| parent | 6530b3f4c5043aa8ef66faa8296291b1ea6ba2eb (diff) | |
| download | lwn-3838cc1850ccd09f93e729e9047ec1995026f83e.tar.gz lwn-3838cc1850ccd09f93e729e9047ec1995026f83e.zip | |
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@linux.vnet.ibm.com>
[ paulmck: Update documentation, as suggested by Josh Triplett. ]
| -rw-r--r-- | Documentation/kernel-parameters.txt | 6 | ||||
| -rw-r--r-- | 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 61ab1628a057..04b811086dca 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 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; } |