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Commit 820687a7 authored by Paul E. McKenney's avatar Paul E. McKenney
Browse files

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: default avatarPaul E. McKenney <paulmck@linux.vnet.ibm.com>
parent b562b85c

Documentation/admin-guide/kernel-parameters.txt

+8 −3
Original line number Diff line number Diff line
@@ -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.

kernel/rcu/rcuperf.c

+3 −0
Original line number Diff line number Diff line
@@ -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) {