chore(memory-connection-limits): fix tests

while addressing the flakiness of the tests I noticed the memory limit was not accurate according to the documentation, documentation mentions the limit [_is reached_](https://github.com/libp2p/rust-libp2p/blob/master/misc/memory-connection-limits/src/lib.rs#L85) not greater than.
This PR fixes that.

To address the flakiness due to now connections being probably a little bit smaller in memory footprint I gave room for a connection threshold in the tests.

Pull-Request: #6134.

Author: jxs

misc/memory-connection-limits/src/lib.rs

@@ -82,7 +82,7 @@ const MAX_STALE_DURATION: Duration = Duration::from_millis(100);
 impl Behaviour {
     /// Sets the process memory usage threshold in absolute bytes.
     ///
-    /// New inbound and outbound connections will be denied when the threshold is reached.
+    /// New inbound and outbound connections will be denied when the threshold is exceeded.
     pub fn with_max_bytes(max_allowed_bytes: usize) -> Self {
         Self {
             max_allowed_bytes,
@@ -95,7 +95,7 @@ impl Behaviour {
 
     /// Sets the process memory usage threshold in the percentage of the total physical memory.
     ///
-    /// New inbound and outbound connections will be denied when the threshold is reached.
+    /// New inbound and outbound connections will be denied when the threshold is exceeded.
     pub fn with_max_percentage(percentage: f64) -> Self {
         use sysinfo::{RefreshKind, System};
 

misc/memory-connection-limits/tests/max_bytes.rs

@@ -31,8 +31,11 @@ use util::*;
 
 #[tokio::test]
 async fn max_bytes() {
+    // These tests use connections as unit to test the memory limit.
+    // Each connection consumes approximately 1MB of memory, so we give
+    // one connection as buffer for test stability (CONNECTION_LIMIT - 1) on line 35.
     const CONNECTION_LIMIT: usize = 20;
-    let max_allowed_bytes = CONNECTION_LIMIT * 1024 * 1024;
+    let max_allowed_bytes = (CONNECTION_LIMIT - 1) * 1024 * 1024;
 
     let mut network = Swarm::new_ephemeral_tokio(|_| TestBehaviour {
         connection_limits: Behaviour::with_max_bytes(max_allowed_bytes),

misc/memory-connection-limits/tests/max_percentage.rs

@@ -59,7 +59,10 @@ async fn max_percentage() {
 
     // Adds current mem usage to the limit and update
     let current_mem = memory_stats::memory_stats().unwrap().physical_mem;
-    let max_allowed_bytes = current_mem + CONNECTION_LIMIT * 1024 * 1024;
+    // These tests use connections as unit to test the memory limit.
+    // Each connection consumes approximately 1MB of memory, so we give
+    // one connection as buffer for test stability (CONNECTION_LIMIT - 1) on line 35.
+    let max_allowed_bytes = current_mem + (CONNECTION_LIMIT - 1) * 1024 * 1024;
     network.behaviour_mut().connection_limits = Behaviour::with_max_percentage(
         max_allowed_bytes as f64 / system_info.total_memory() as f64,
     );