rcuperf: Add writer_holdoff boot parameter
This commit adds a writer_holdoff boot parameter to rcuperf, which is
intended to be used to test Tree SRCU's auto-expediting. This
boot parameter is in microseconds, and defaults to zero (that is,
disabled). Set it to a bit larger than srcutree.exp_holdoff,
keeping the nanosecond/microsecond conversion, to force Tree SRCU
to auto-expedite more aggressively.
This commit also adds documentation for this parameter, and fixes some
alphabetization while in the neighborhood.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 3598464..01b5ab9 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -3357,17 +3357,22 @@
rcuperf.perf_runnable= [BOOT]
Start rcuperf running at boot time.
+ rcuperf.perf_type= [KNL]
+ Specify the RCU implementation to test.
+
rcuperf.shutdown= [KNL]
Shut the system down after performance tests
complete. This is useful for hands-off automated
testing.
- rcuperf.perf_type= [KNL]
- Specify the RCU implementation to test.
-
rcuperf.verbose= [KNL]
Enable additional printk() statements.
+ rcuperf.writer_holdoff= [KNL]
+ Write-side holdoff between grace periods,
+ in microseconds. The default of zero says
+ no holdoff.
+
rcutorture.cbflood_inter_holdoff= [KNL]
Set holdoff time (jiffies) between successive
callback-flood tests.
diff --git a/kernel/rcu/rcuperf.c b/kernel/rcu/rcuperf.c
index 49c8ed6..d80f11d 100644
--- a/kernel/rcu/rcuperf.c
+++ b/kernel/rcu/rcuperf.c
@@ -68,6 +68,7 @@ torture_param(int, nwriters, -1, "Number of RCU updater threads");
torture_param(bool, shutdown, !IS_ENABLED(MODULE),
"Shutdown at end of performance tests.");
torture_param(bool, verbose, true, "Enable verbose debugging printk()s");
+torture_param(int, writer_holdoff, 0, "Holdoff (us) between GPs, zero to disable");
static char *perf_type = "rcu";
module_param(perf_type, charp, 0444);
@@ -447,6 +448,8 @@ rcu_perf_writer(void *arg)
}
do {
+ if (writer_holdoff)
+ udelay(writer_holdoff);
wdp = &wdpp[i];
*wdp = ktime_get_mono_fast_ns();
if (gp_async) {