Limit Rayon threadpool threads (#5871)

local_cluster/src/local_cluster.rs

@@ -10,6 +10,7 @@ use solana_core::{
     service::Service,
     validator::{Validator, ValidatorConfig},
 };
+use solana_rayon_threadlimit::set_thread_count;
 use solana_sdk::{
     client::SyncClient,
     clock::DEFAULT_TICKS_PER_SLOT,
@@ -116,6 +117,8 @@ impl LocalCluster {
     }
 
     pub fn new(config: &ClusterConfig) -> Self {
+        set_thread_count(1);
+
         assert_eq!(config.validator_configs.len(), config.node_stakes.len());
         let leader_keypair = Arc::new(Keypair::new());
         let leader_pubkey = leader_keypair.pubkey();