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| author |   Paul E. McKenney <paulmck@kernel.org> | 2020-05-25 09:22:24 -0700 |
|---|---|---|
| committer | Paul E. McKenney <paulmck@kernel.org> | 2020-06-29 12:00:44 -0700 |
| commit | 708cda31652c02e64adaeafafe7b996e4e14c3eb (patch) | |
| tree | caf00c4d6860aca00b306e7905e8bc0d010d5040 /kernel/rcu/rcuperf.c | |
| parent | refperf: Add a test to measure performance of read-side synchronization (diff) | |
| download | wireguard-linux-708cda31652c02e64adaeafafe7b996e4e14c3eb.tar.xz wireguard-linux-708cda31652c02e64adaeafafe7b996e4e14c3eb.zip | |
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: Paul E. McKenney <paulmck@kernel.org>
Diffstat (limited to 'kernel/rcu/rcuperf.c')
| -rw-r--r-- | kernel/rcu/rcuperf.c | 11 |
1 files changed, 9 insertions, 2 deletions
diff --git a/kernel/rcu/rcuperf.c b/kernel/rcu/rcuperf.c index 246da8fe199e..d906ca987936 100644 --- a/kernel/rcu/rcuperf.c +++ b/kernel/rcu/rcuperf.c @@ -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) |