Customers using GKE 1.25 and 1.26 are facing conntrack issues
root caused to commit c9c3b6811f74 ("netfilter: conntrack: make
max chain length random").
Even if we assume Uniform Hashing, a bucket often reachs 8 chained
items while the load factor of the hash table is smaller than 0.5
With a limit of 16, we reach load factors of 3.
With a limit of 32, we reach load factors of 11.
With a limit of 40, we reach load factors of 15.
With a limit of 50, we reach load factors of 24.
This patch changes MIN_CHAINLEN to 50, to minimize risks.
Ideally, we could in the future add a cushion based on expected
load factor (2 * nf_conntrack_max / nf_conntrack_buckets),
because some setups might expect unusual values.
Fixes: c9c3b6811f74 ("netfilter: conntrack: make max chain length random")
Signed-off-by: Eric Dumazet <edumazet@xxxxxxxxxx>
---
net/netfilter/nf_conntrack_core.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/net/netfilter/nf_conntrack_core.c b/net/netfilter/nf_conntrack_core.c
index 7250082e7de56c77298b0d3b62c4f0dff95b77cc..c6a6a6099b4e2200951367ccd90c12c0ac800a6a 100644
--- a/net/netfilter/nf_conntrack_core.c
+++ b/net/netfilter/nf_conntrack_core.c
@@ -96,8 +96,8 @@ static DEFINE_MUTEX(nf_conntrack_mutex);
#define GC_SCAN_MAX_DURATION msecs_to_jiffies(10)
#define GC_SCAN_EXPIRED_MAX (64000u / HZ)
-#define MIN_CHAINLEN 8u
-#define MAX_CHAINLEN (32u - MIN_CHAINLEN)
+#define MIN_CHAINLEN 50u
+#define MAX_CHAINLEN (80u - MIN_CHAINLEN)
static struct conntrack_gc_work conntrack_gc_work;
--
2.40.0.rc0.216.gc4246ad0f0-goog
