[DTrace-devel] [PATCH] test: fix speculation/tst.SingleCPU.d

[Nick Alcock]

This test is meant to verify that simultaneously-active speculations get
drained and committed/discarded appropriately without losing any of
them.  Unfortunately, it never sets nspec, which is 1 by default, so it
actually runs out of speculations almost immediately: we need at least
16 for this test, which is not so coincidentally the maximum this
implementation supports right now.  Boosting that reveals another
problem: we print out the speculation ID, which is not in any sense a
guaranteed value, so we get lots of test failures: what we *actually*
care about is that the n value printed is suitable (indicating that the
first speculation in any block of (64 / 4) was committed and the rest
were discarded, and who cares what its ID is).

We also knock the switchrate down to 1ms again because if we knock it up
any higher the discards (which are processed in userspace) don't get
processed fast enough to keep up, and we run out.  We consume 16
speculations in 6.4ms, so set the switchrate to 3ms to give us a bit of
headroom.  (This will still be racy on highly-loaded test systems where
the polls just don't happen fast enough because of system load: if that
happens, we can tag the test suitably in future.)

Signed-off-by: Nick Alcock <nick.alcock at oracle.com>
---
 test/unittest/speculation/tst.SingleCPU.d |  4 ++-
 test/unittest/speculation/tst.SingleCPU.r | 32 +++++++++++------------
 2 files changed, 19 insertions(+), 17 deletions(-)

diff --git a/test/unittest/speculation/tst.SingleCPU.d b/test/unittest/speculation/tst.SingleCPU.d
index 81a5afa100b9b..dd68db1a1f380 100644
--- a/test/unittest/speculation/tst.SingleCPU.d
+++ b/test/unittest/speculation/tst.SingleCPU.d
@@ -13,6 +13,8 @@
 /* @@trigger: bogus-ioctl */
 
 #pragma D option quiet
+#pragma D option nspec=16
+#pragma D option switchrate=3ms
 
 BEGIN
 {
@@ -37,7 +39,7 @@ syscall::ioctl:entry
 / pid == $target && (n & 3) == 1 /
 {
 	speculate(i);
-	printf("%4d %4d", n, i);
+	printf("%4d", n);
 }
 
 syscall::ioctl:entry
diff --git a/test/unittest/speculation/tst.SingleCPU.r b/test/unittest/speculation/tst.SingleCPU.r
index 3659925d10b0f..66740b74ddf21 100644
--- a/test/unittest/speculation/tst.SingleCPU.r
+++ b/test/unittest/speculation/tst.SingleCPU.r
@@ -1,17 +1,17 @@
-   1    1   2 hello world
-  65    1  66 hello world
- 129    1 130 hello world
- 193    1 194 hello world
- 257    1 258 hello world
- 321    1 322 hello world
- 385    1 386 hello world
- 449    1 450 hello world
- 513    1 514 hello world
- 577    1 578 hello world
- 641    1 642 hello world
- 705    1 706 hello world
- 769    1 770 hello world
- 833    1 834 hello world
- 897    1 898 hello world
- 961    1 962 hello world
+   1   2 hello world
+  65  66 hello world
+ 129 130 hello world
+ 193 194 hello world
+ 257 258 hello world
+ 321 322 hello world
+ 385 386 hello world
+ 449 450 hello world
+ 513 514 hello world
+ 577 578 hello world
+ 641 642 hello world
+ 705 706 hello world
+ 769 770 hello world
+ 833 834 hello world
+ 897 898 hello world
+ 961 962 hello world
 
-- 
2.39.0