Commit 708cda31 authored by Paul E. McKenney's avatar Paul E. McKenney
Browse files

rcuperf: Add comments explaining the high reader overhead 



This commit adds comments explaining why the readers have otherwise insane
levels of measurement overhead, namely that they are intended as a test
load for update-side performance measurements, not as a straight-up
read-side performance test.

Signed-off-by: default avatarPaul E. McKenney <paulmck@kernel.org>
parent 653ed64b

kernel/rcu/rcuperf.c

+9 −2
Original line number Diff line number Diff line
@@ -69,6 +69,11 @@ MODULE_AUTHOR("Paul E. McKenney <paulmck@linux.ibm.com>"); 
 *	value specified by nr_cpus for a read-only test.

 *

 * Various other use cases may of course be specified.

 *

 * Note that this test's readers are intended only as a test load for

 * the writers.  The reader performance statistics will be overly

 * pessimistic due to the per-critical-section interrupt disabling,

 * test-end checks, and the pair of calls through pointers.

 */



#ifdef MODULE
@@ -309,8 +314,10 @@ static void rcu_perf_wait_shutdown(void) 
}



/*

 * RCU perf reader kthread.  Repeatedly does empty RCU read-side

 * critical section, minimizing update-side interference.

 * RCU perf reader kthread.  Repeatedly does empty RCU read-side critical

 * section, minimizing update-side interference.  However, the point of

 * this test is not to evaluate reader performance, but instead to serve

 * as a test load for update-side performance testing.

 */

static int

rcu_perf_reader(void *arg)

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