Add validator option to change niceness of snapshot packager thread

clap-utils/Cargo.toml

@@ -12,6 +12,7 @@ edition = "2018"
 [dependencies]
 clap = "2.33.0"
 rpassword = "5.0"
+solana-perf = { path = "../perf", version = "=1.9.0" }
 solana-remote-wallet = { path = "../remote-wallet", version = "=1.9.0" }
 solana-sdk = { path = "../sdk", version = "=1.9.0" }
 thiserror = "1.0.30"

clap-utils/src/input_validators.rs

@@ -370,6 +370,27 @@ where
     }
 }
 
+pub fn is_niceness_adjustment_valid<T>(value: T) -> Result<(), String>
+where
+    T: AsRef<str> + Display,
+{
+    let adjustment = value.as_ref().parse::<i8>().map_err(|err| {
+        format!(
+            "error parsing niceness adjustment value '{}': {}",
+            value, err
+        )
+    })?;
+    if solana_perf::thread::is_renice_allowed(adjustment) {
+        Ok(())
+    } else {
+        Err(String::from(
+            "niceness adjustment supported only on Linux; negative adjustment \
+             (priority increase) requires root or CAP_SYS_NICE (see `man 7 capabilities` \
+             for details)",
+        ))
+    }
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
@@ -386,4 +407,11 @@ mod tests {
         assert!(is_derivation("a/b").is_err());
         assert!(is_derivation("0/4294967296").is_err());
     }
+
+    #[test]
+    fn test_is_niceness_adjustment_valid() {
+        assert_eq!(is_niceness_adjustment_valid("0"), Ok(()));
+        assert!(is_niceness_adjustment_valid("128").is_err());
+        assert!(is_niceness_adjustment_valid("-129").is_err());
+    }
 }