diff mbox series

[RFT,2/2] rte_pie: fix incorrect floating point math

Message ID 20220524184623.480646-3-stephen@networkplumber.org (mailing list archive)
State Superseded, archived
Delegated to: Thomas Monjalon
Headers
Series pie: floating point fixes |

Checks

Context Check Description
ci/checkpatch success coding style OK
ci/iol-aarch64-unit-testing fail Testing issues
ci/iol-mellanox-Performance success Performance Testing PASS
ci/iol-intel-Performance success Performance Testing PASS
ci/iol-intel-Functional success Functional Testing PASS
ci/github-robot: build fail github build: failed
ci/iol-aarch64-compile-testing fail Testing issues
ci/iol-x86_64-unit-testing fail Testing issues
ci/Intel-compilation fail Compilation issues
ci/intel-Testing success Testing PASS
ci/iol-abi-testing success Testing PASS
ci/iol-x86_64-compile-testing fail Testing issues

Commit Message

Stephen Hemminger May 24, 2022, 6:46 p.m. UTC 
  The function rte_pie_drop was attempting to do a random probability
drop, but because of incorrect usage of fixed point divide
it would always return 1.

Change to use multiply to compute the probability.
Fixes: 44c730b0e379 ("sched: add PIE based congestion management")
Cc: wojciechx.liguzinski@intel.com
Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
---
 lib/sched/rte_pie.h | 5 +----
 1 file changed, 1 insertion(+), 4 deletions(-)
diff mbox series

Patch

diff --git a/lib/sched/rte_pie.h b/lib/sched/rte_pie.h
index 3e2c1ef46721..82e6a05645a6 100644
--- a/lib/sched/rte_pie.h
+++ b/lib/sched/rte_pie.h
@@ -217,7 +217,6 @@  __rte_experimental
 _rte_pie_drop(const struct rte_pie_config *pie_cfg,
 	struct rte_pie *pie)
 {
-	uint64_t rand_value;
 	uint64_t qdelay = pie_cfg->qdelay_ref / 2;
 
 	/* PIE is active but the queue is not congested: return 0 */
@@ -240,9 +239,7 @@  _rte_pie_drop(const struct rte_pie_config *pie_cfg,
 	if (pie->accu_prob >= 8.5)
 		return 1;
 
-	rand_value = rte_rand()/RTE_RAND_MAX;
-
-	if ((double)rand_value < pie->drop_prob) {
+	if (rte_rand() < (uint64_t)RTE_RAND_MAX * pie->drop_prob) {
 		pie->accu_prob = 0;
 		return 1;
 	}