Decrease MAX_VERIFIERS

In current structure, multithreading helps little. Because the verification step should be sequential.

Author: HoOngEe

core/src/verification/queue/mod.rs

@@ -37,7 +37,7 @@ const MIN_MEM_LIMIT: usize = 16384;
 const MIN_QUEUE_LIMIT: usize = 512;
 
 // maximum possible number of verification threads.
-const MAX_VERIFIERS: usize = 8;
+const MAX_VERIFIERS: usize = 2;
 
 /// Type alias for block queue convenience.
 pub type BlockQueue = VerificationQueue<kind::Blocks>;
@@ -150,7 +150,7 @@ impl<K: Kind> VerificationQueue<K> {
         let empty = Arc::new(SCondvar::new());
         let more_to_verify = Arc::new(SCondvar::new());
 
-        let num_verifiers = cmp::min(num_cpus::get(), MAX_VERIFIERS);
+        let num_verifiers = MAX_VERIFIERS;
         let mut verifier_handles = Vec::with_capacity(num_verifiers);
 
         for i in 0..num_verifiers {