emc_conditional_insert uses pmd->last_cycles and the packet's RSS hash
to generate a random number used to determine whether or not an emc
entry should be inserted. This works for single-packet bursts as
last_cycles is updated for each burst. However, for bursts > 1 packet,
where the packets in the batch generate the same RSS hash,
pmd->last_cycles remains constant for the entire burst also, and thus
cannot be used as a random number for each packet in the burst.
This commit replaces the use of pmd->last_cycles with random_uint32()
for this purpose and subsequently fixes the behavior of the
emc_insert_inv_prob setting for high-throughput (large bursts)
single-flow cases.
Fixes: 4c30b24602c3 ("dpif-netdev: Conditional EMC insert")
Reported-by: Kevin Traynor <[email protected]>
Acked-by: Darrell Ball <[email protected]>
Signed-off-by: Ciara Loftus <[email protected]>
---
v2:
- Remove unnecessary ORing in random number calcuation as per Ben's
suggestion.
v3:
- Coding standards fix
lib/dpif-netdev.c | 6 +-----
1 file changed, 1 insertion(+), 5 deletions(-)
diff --git a/lib/dpif-netdev.c b/lib/dpif-netdev.c
index 4e29085..2dbdd47 100644
--- a/lib/dpif-netdev.c
+++ b/lib/dpif-netdev.c
@@ -2073,11 +2073,7 @@ emc_probabilistic_insert(struct dp_netdev_pmd_thread
*pmd,
uint32_t min;
atomic_read_relaxed(&pmd->dp->emc_insert_min, &min);
-#ifdef DPDK_NETDEV
- if (min && (key->hash ^ (uint32_t) pmd->last_cycles) <= min) {
-#else
- if (min && (key->hash ^ random_uint32()) <= min) {
-#endif
+ if (min && random_uint32() <= min) {
emc_insert(&pmd->flow_cache, key, flow);
}
}
--
2.4.11
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