[PATCH tip/core/rcu 08/30] refperf: Convert nreaders to a module parameter

paulmck
2020-06-23T00:32:13Z

This commit converts nreaders to a module parameter, with the default
of -1 specifying the old behavior of using 75% of the readers.

Cc: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
kernel/rcu/refperf.c | 16 +++++++++++-----
1 file changed, 11 insertions(+), 5 deletions(-)

diff --git a/kernel/rcu/refperf.c b/kernel/rcu/refperf.c
index e991d48..020e55a 100644
--- a/kernel/rcu/refperf.c
+++ b/kernel/rcu/refperf.c
@@ -62,6 +62,12 @@ torture_param(int, holdoff, IS_BUILTIN(CONFIG_RCU_REF_PERF_TEST) ? 10 : 0,
"Holdoff time before test start (s)");
// Number of loops per experiment, all readers execute operations concurrently.
torture_param(long, loops, 10000000, "Number of loops per experiment.");
+// Number of readers, with -1 defaulting to about 75% of the CPUs.
+torture_param(int, nreaders, -1, "Number of readers, -1 for 75% of CPUs.");
+// Number of runs.
+torture_param(int, nruns, 30, "Number of experiments to run.");
+// Reader delay in nanoseconds, 0 for no delay.
+torture_param(int, readdelay, 0, "Read-side delay in nanoseconds.");

#ifdef MODULE
# define REFPERF_SHUTDOWN 0
@@ -93,7 +99,6 @@ static wait_queue_head_t main_wq;
static int shutdown_start;

static struct reader_task *reader_tasks;
-static int nreaders;

// Number of readers that are part of the current experiment.
static atomic_t nreaders_exp;
@@ -411,8 +416,8 @@ static void
ref_perf_print_module_parms(struct ref_perf_ops *cur_ops, const char *tag)
{
pr_alert("%s" PERF_FLAG
- "--- %s: verbose=%d shutdown=%d holdoff=%d loops=%ld\n", perf_type, tag,
- verbose, shutdown, holdoff, loops);
+ "--- %s: verbose=%d shutdown=%d holdoff=%d loops=%ld nreaders=%d\n", perf_type, tag,
+ verbose, shutdown, holdoff, loops, nreaders);
}

static void
@@ -501,8 +506,9 @@ ref_perf_init(void)
schedule_timeout_uninterruptible(1);
}

- // Reader tasks (~75% of online CPUs).
- nreaders = (num_online_cpus() >> 1) + (num_online_cpus() >> 2);
+ // Reader tasks (default to ~75% of online CPUs).
+ if (nreaders < 0)
+ nreaders = (num_online_cpus() >> 1) + (num_online_cpus() >> 2);
reader_tasks = kcalloc(nreaders, sizeof(reader_tasks[0]),
GFP_KERNEL);
if (!reader_tasks) {
--
2.9.5