Get reference gas price (MystenLabs#10373)

## Description 

Use `num_chunks_per_thread` to control how many calls we make per client
per thread

## Test Plan 

How did you test the new or updated feature?

---
If your changes are not user-facing and not a breaking change, you can
skip the following section. Otherwise, please indicate what changed, and
then add to the Release Notes section as highlighted during the release
process.

### Type of Change (Check all that apply)

- [ ] user-visible impact
- [ ] breaking change for a client SDKs
- [ ] breaking change for FNs (FN binary must upgrade)
- [ ] breaking change for validators or node operators (must upgrade
binaries)
- [ ] breaking change for on-chain data layout
- [ ] necessitate either a data wipe or data migration

### Release notes

crates/sui-rpc-loadgen/README.md

@@ -64,6 +64,11 @@ cargo run --bin sui-rpc-loadgen -- --urls "http://127.0.0.1:9000" "http://127.0.
 cargo run --bin sui-rpc-loadgen -- --urls "http://127.0.0.1:9000" "http://127.0.0.1:9000" --num-threads 4 get-all-balances
 ```
 
+### Get Reference Gas Price
+```bash
+cargo run --bin sui-rpc-loadgen -- --urls "http://127.0.0.1:9000" "http://127.0.0.1:9000" --num-threads 4 get-reference-gas-price --num-chunks-per-thread 10
+```
+
 # Useful commands
 
 ```bash

crates/sui-rpc-loadgen/src/main.rs

@@ -111,6 +111,11 @@ pub enum ClapCommand {
         #[clap(flatten)]
         common: CommonOptions,
     },
+    #[clap(name = "get-reference-gas-price")]
+    GetReferenceGasPrice {
+        #[clap(flatten)]
+        common: CommonOptions,
+    },
 }
 
 fn get_keypair() -> Result<SignerInfo> {
@@ -206,6 +211,14 @@ async fn main() -> Result<(), Box<dyn Error>> {
             let objects = load_objects_from_file(expand_path(&opts.data_directory));
             (Command::new_multi_get_objects(objects), common, false)
         }
+        ClapCommand::GetReferenceGasPrice { common } => {
+            let num_repeats = common.num_chunks_per_thread;
+            (
+                Command::new_get_reference_gas_price(num_repeats),
+                common,
+                false,
+            )
+        }
     };
 
     let signer_info = need_keystore.then_some(get_keypair()?);

crates/sui-rpc-loadgen/src/payload/get_reference_gas_price.rs

@@ -0,0 +1,40 @@
+// Copyright (c) Mysten Labs, Inc.
+// SPDX-License-Identifier: Apache-2.0
+
+use anyhow::Result;
+use futures::future::try_join_all;
+use sui_sdk::SuiClient;
+
+use crate::payload::{GetReferenceGasPrice, ProcessPayload, RpcCommandProcessor, SignerInfo};
+use async_trait::async_trait;
+
+#[async_trait]
+impl<'a> ProcessPayload<'a, &'a GetReferenceGasPrice> for RpcCommandProcessor {
+    async fn process(
+        &'a self,
+        op: &'a GetReferenceGasPrice,
+        _signer_info: &Option<SignerInfo>,
+    ) -> Result<()> {
+        let clients = self.get_clients().await?;
+
+        let futures = (0..op.num_repeats).map(|_| {
+            let clients = clients.clone();
+            async move {
+                let futures = clients.iter().map(get_reference_gas_price);
+                try_join_all(futures).await
+            }
+        });
+
+        try_join_all(futures).await.unwrap();
+        Ok(())
+    }
+}
+
+async fn get_reference_gas_price(client: &SuiClient) -> Result<u64> {
+    let results = client
+        .governance_api()
+        .get_reference_gas_price()
+        .await
+        .unwrap();
+    Ok(results)
+}

crates/sui-rpc-loadgen/src/payload/mod.rs

@@ -4,6 +4,7 @@
 mod checkpoint_utils;
 mod get_all_balances;
 mod get_checkpoints;
+mod get_reference_gas_price;
 mod multi_get_objects;
 mod pay_sui;
 mod query_transactions;
@@ -123,6 +124,14 @@ impl Command {
         }
     }
 
+    pub fn new_get_reference_gas_price(num_repeats: usize) -> Self {
+        let get_reference_gas_price = GetReferenceGasPrice { num_repeats };
+        Self {
+            data: CommandData::GetReferenceGasPrice(get_reference_gas_price),
+            ..Default::default()
+        }
+    }
+
     pub fn with_repeat_n_times(mut self, num: usize) -> Self {
         self.repeat_n_times = num;
         self
@@ -143,6 +152,7 @@ pub enum CommandData {
     QueryTransactionBlocks(QueryTransactionBlocks),
     MultiGetObjects(MultiGetObjects),
     GetAllBalances(GetAllBalances),
+    GetReferenceGasPrice(GetReferenceGasPrice),
 }
 
 impl Default for CommandData {
@@ -198,6 +208,11 @@ pub struct GetAllBalances {
     pub addresses: Vec<SuiAddress>,
 }
 
+#[derive(Clone)]
+pub struct GetReferenceGasPrice {
+    num_repeats: usize,
+}
+
 #[async_trait]
 pub trait Processor {
     /// process commands in order

crates/sui-rpc-loadgen/src/payload/rpc_command_processor.rs

@@ -82,6 +82,7 @@ impl RpcCommandProcessor {
             CommandData::QueryTransactionBlocks(ref v) => self.process(v, signer_info).await,
             CommandData::MultiGetObjects(ref v) => self.process(v, signer_info).await,
             CommandData::GetAllBalances(ref v) => self.process(v, signer_info).await,
+            CommandData::GetReferenceGasPrice(ref v) => self.process(v, signer_info).await,
         }
     }