Added a disk benchmark test for sequential reads

src/main.rs

@@ -28,7 +28,15 @@ struct Disk {
 
 #[derive(Subcommand)]
 enum DiskCommands {
-    #[clap(name = "write-test", about = "Write a large file to determine sequential disk speeds.")]
+    // disk read subcommand
+    #[clap(name = "read-test", about = "Read from /dev/zero to determine sequential disk read speeds.")]
+    ReadTest {
+        #[clap(short = 's', default_value_t = 15)]
+        size: u8,
+    },
+
+    // disk write subcommand
+    #[clap(name = "write-test", about = "Write a large file to determine sequential disk write speeds.")]
     WriteTest {
         #[clap(short = 't', default_value_t = String::from("/tmp/disk-test.tmp"))]
         tempfile: String,
@@ -70,6 +78,7 @@ fn main() {
     // map subcommands back to the main command
     match &cli.command {
         Commands::Disk(args) => match &args.disk_commands {
+            DiskCommands::ReadTest { size } => tests::disk::disk_read_test(size),
             DiskCommands::WriteTest { tempfile, size } => tests::disk::disk_write_test(tempfile, size),
         }
 

src/tests/disk.rs

@@ -1,6 +1,33 @@
 use std::fs;
 use std::process::Command;
 
+// test disk read speeds by reading for /dev/zero and writing it to /dev/null
+pub fn disk_read_test(size: &u8) {
+    // convert size in Gigabytes down to Megabytes
+    let size_gigs: u32 = (*size as u32 * 1024 * 8).into();
+
+    // run sync to clear out any disk caches prior to running
+    Command::new("sync");
+
+    // run the dd command
+    let output = Command::new("dd")
+        .arg("bs=128k")
+        .arg(format!("count={}", size_gigs))
+        .arg("if=/dev/zero")
+        .arg("of=/dev/null")
+        .output()
+        .expect("Failed to execute command");
+
+    // check that the command succeeded
+    assert!(output.status.success());
+
+    // dd's output ends up in stderr
+    println!("{}", String::from_utf8_lossy(&output.stderr));
+
+    // run another sync to clear out the disk's cache
+    Command::new("sync");
+}
+
 // test disk write speeds by continually writing zeroes to it
 pub fn disk_write_test(tempfile: &str, size: &u8) {
     // convert size in Gigabytes down to Megabytes