Optimize genesis JSON reading about nearcore HOT 8 CLOSED

diff --git a/Cargo.lock b/Cargo.lock
index 28e7bd264..1834ab4aa 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -3505,6 +3505,7 @@ dependencies = [
  "anyhow",
  "chrono",
  "derive_more",
+ "memmap2",
  "near-config-utils",
  "near-crypto",
  "near-o11y",
@@ -3645,6 +3646,7 @@ version = "0.0.0"
 dependencies = [
  "anyhow",
  "json_comments",
+ "memmap2",
  "thiserror",
  "tracing",
 ]
diff --git a/core/chain-configs/Cargo.toml b/core/chain-configs/Cargo.toml
index 1c59b650c..d0c99ff7a 100644
--- a/core/chain-configs/Cargo.toml
+++ b/core/chain-configs/Cargo.toml
@@ -14,6 +14,7 @@ anyhow.workspace = true
 chrono.workspace = true
 derive_more.workspace = true
 num-rational.workspace = true
+memmap2.workspace = true
 once_cell.workspace = true
 serde.workspace = true
 serde_json.workspace = true
@@ -31,10 +32,6 @@ nightly_protocol = [
   "near-o11y/nightly_protocol",
   "near-primitives/nightly_protocol",
 ]
-nightly = [
-  "nightly_protocol",
-  "near-o11y/nightly",
-  "near-primitives/nightly",
-]
+nightly = ["nightly_protocol", "near-o11y/nightly", "near-primitives/nightly"]
 default = []
 metrics = ["near-o11y"]
diff --git a/core/chain-configs/src/genesis_config.rs b/core/chain-configs/src/genesis_config.rs
index 1df019aa6..d56fa53a2 100644
--- a/core/chain-configs/src/genesis_config.rs
+++ b/core/chain-configs/src/genesis_config.rs
@@ -531,33 +531,45 @@ impl Genesis {
         path: P,
         genesis_validation: GenesisValidationMode,
     ) -> Result<Self, ValidationError> {
-        let mut file = File::open(&path).map_err(|_| ValidationError::GenesisFileError {
+        use std::time::Instant;
+        let now = Instant::now();
+        let file = File::open(&path).map_err(|_| ValidationError::GenesisFileError {
             error_message: format!(
                 "Could not open genesis config file at path {}.",
                 &path.as_ref().display()
             ),
         })?;
+        use memmap2::MmapOptions;
+        let mmap = unsafe {
+            MmapOptions::new().map(&file).map_err(|_| ValidationError::GenesisFileError {
+                error_message: format!(
+                    "Could not mmap genesis config file at path {}.",
+                    &path.as_ref().display()
+                ),
+            })?
+        };

-        let mut json_str = String::new();
-        file.read_to_string(&mut json_str).map_err(|_| ValidationError::GenesisFileError {
-            error_message: format!("Failed to read genesis config file to string. "),
-        })?;
+        // let striper = near_config_utils::strip_comments_from_mmap(&mmap);

-        let json_str_without_comments = near_config_utils::strip_comments_from_json_str(&json_str)
-            .map_err(|_| ValidationError::GenesisFileError {
-                error_message: format!("Failed to strip comments from genesis config file"),
-            })?;
+        // let genesis =
+        //     serde_json::from_reader::<near_config_utils::StripComments<&[u8]>, Genesis>(striper)
+        //         .map_err(|_| ValidationError::GenesisFileError {
+        //             error_message: format!("Failed to deserialize the genesis records."),
+        //         })?;
+        let genesis = serde_json::from_slice::<Genesis>(&mmap).map_err(|_| {
+            ValidationError::GenesisFileError {
+                error_message: format!("Failed to deserialize the genesis records."),
+            }
+        })?;

-        let genesis =
-            serde_json::from_str::<Genesis>(&json_str_without_comments).map_err(|_| {
-                ValidationError::GenesisFileError {
-                    error_message: format!("Failed to deserialize the genesis records."),
-                }
-            })?;
+        let elapsed = now.elapsed();
+        println!("Elapsed: {:.2?}", elapsed);

         genesis.validate(genesis_validation)?;
         Ok(genesis)
     }
+    /// Reads Genesis from a single JSON file, the file can't be JSON with comments
+    /// This function will collect all errors regarding genesis.json and push them to validation_errors

     /// Reads Genesis from config and records files.
     pub fn from_files<P1, P2>(
diff --git a/utils/config/Cargo.toml b/utils/config/Cargo.toml
index 6fd62fc75..f987fbe22 100644
--- a/utils/config/Cargo.toml
+++ b/utils/config/Cargo.toml
@@ -14,4 +14,4 @@ anyhow.workspace = true
 json_comments.workspace = true
 thiserror.workspace = true
 tracing.workspace = true
-
+memmap2.workspace = true
diff --git a/utils/config/src/lib.rs b/utils/config/src/lib.rs
index a8f15c61c..990d59edd 100644
--- a/utils/config/src/lib.rs
+++ b/utils/config/src/lib.rs
@@ -1,6 +1,7 @@
 use std::io::Read;

-use json_comments::StripComments;
+pub use json_comments::StripComments;
+use memmap2::Mmap;

 // strip comments from a JSON string with comments.
 // the comment formats that are supported: //, /* */ and #.
@@ -16,6 +17,9 @@ pub fn strip_comments_from_json_str(json_str: &String) -> std::io::Result<String
 pub fn strip_comments_from_json_reader(reader: impl Read) -> impl Read {
     StripComments::new(reader)
 }
+pub fn strip_comments_from_mmap<'a>(reader: &'a Mmap) -> StripComments<&'a [u8]> {
+    StripComments::new(reader.as_ref())
+}

 /// errors that arise when loading config files or config semantic checks
 /// config files here include: genesis.json, config.json, node_key.json, validator_key.json