Refine the implementation of NiceValue

src/libos/src/fs/procfs/pid/stat.rs

@@ -36,8 +36,9 @@ impl ProcINode for ProcStatINode {
         let stime = 0;
         let cutime = 0;
         let cstime = 0;
-        let priority = main_thread.nice().read().unwrap().to_priority_val();
-        let nice = main_thread.nice().read().unwrap().raw_val();
+        // Convert [19,-20] to [39,0].
+        let priority = main_thread.nice().read().unwrap().to_raw_val() + 20;
+        let nice = main_thread.nice().read().unwrap().to_raw_val();
         let num_threads = self.0.threads().len();
         let itrealvalue = 0;
         let starttime = self.0.start_time();

src/libos/src/process/thread/mod.rs

@@ -42,6 +42,9 @@ pub struct Thread {
     fs: FsViewRef,
     files: FileTableRef,
     sched: SchedAgentRef,
+    // According to POSIX, the nice value is a per-process setting.
+    // In our implementation, the threads belong to same process
+    // share the same nice value.
     nice: NiceValueRef,
     rlimits: ResourceLimitsRef,
     // Signal

src/libos/src/sched/do_priority.rs

@@ -2,18 +2,17 @@ use super::priority::{NiceValue, PrioWhich};
 use crate::prelude::*;
 use crate::process::table::{get_all_processes, get_pgrp, get_process};
 
-pub fn do_set_priority(which: PrioWhich, who: i32, prio: NiceValue) -> Result<()> {
+pub fn do_set_priority(which: PrioWhich, who: i32, nice: NiceValue) -> Result<()> {
     debug!(
-        "set_priority: which: {:?}, who: {}, prio: {:?}",
-        which, who, prio
+        "set_priority: which: {:?}, who: {}, nice: {:?}",
+        which, who, nice
     );
 
     let processes = get_processes(which, who)?;
     for process in processes.iter() {
-        let main_thread = process
-            .main_thread()
-            .ok_or_else(|| errno!(ESRCH, "invalid pid"))?;
-        *main_thread.nice().write().unwrap() = prio;
+        for thread in process.threads().iter() {
+            *thread.nice().write().unwrap() = nice;
+        }
     }
     Ok(())
 }
@@ -22,27 +21,25 @@ pub fn do_get_priority(which: PrioWhich, who: i32) -> Result<NiceValue> {
     debug!("get_priority: which: {:?}, who: {}", which, who);
 
     let processes = get_processes(which, who)?;
-    let prio = {
-        let mut prio = NiceValue::max_value();
+    let nice = {
+        let mut nice = NiceValue::MAX;
         for process in processes.iter() {
             let main_thread = process
                 .main_thread()
                 .ok_or_else(|| errno!(ESRCH, "invalid pid"))?;
-            let nice_value = main_thread.nice().read().unwrap();
+            let current_nice = main_thread.nice().read().unwrap();
             // Returns the highest priority enjoyed by the processes
-            if *nice_value < prio {
-                prio = *nice_value;
+            if *current_nice < nice {
+                nice = *current_nice;
             }
         }
-        prio
+        nice
     };
-    Ok(prio)
+    Ok(nice)
 }
 
-// According to POSIX, the nice value is a per-process setting.
-// In our implementation, the threads belong to same process share the same nice value.
 fn get_processes(which: PrioWhich, who: i32) -> Result<Vec<crate::process::ProcessRef>> {
-    Ok(match which {
+    let processes = match which {
         PrioWhich::PRIO_PROCESS => {
             let process = if who == 0 {
                 current!().process().clone()
@@ -67,5 +64,10 @@ fn get_processes(which: PrioWhich, who: i32) -> Result<Vec<crate::process::Proce
                 return_errno!(ESRCH, "no such user");
             }
         }
-    })
+    };
+    if processes.is_empty() {
+        return_errno!(ESRCH, "no such process");
+    }
+
+    Ok(processes)
 }

src/libos/src/sched/priority.rs

@@ -21,55 +21,48 @@ impl TryFrom<i32> for PrioWhich {
     }
 }
 
-/// Process priority value
+/// Process scheduling nice value.
 ///
 /// Lower values give a process a higher scheduling priority.
 #[derive(Copy, Clone, Debug, Default, PartialEq, PartialOrd)]
 pub struct NiceValue {
-    value: i32,
+    value: i8,
 }
 
 impl NiceValue {
-    const MAX_PRIO: i32 = 19;
+    pub const MAX: Self = Self { value: 19 };
 
-    const MIN_PRIO: i32 = -20;
+    pub const MIN: Self = Self { value: -20 };
 
-    pub fn max_value() -> Self {
-        Self {
-            value: Self::MAX_PRIO,
+    /// Create a nice value from a raw value.
+    ///
+    /// The raw value given beyond the range are automatically adjusted
+    /// to the nearest boundary value.
+    pub fn new(raw: i8) -> Self {
+        if raw < Self::MIN.value {
+            Self::MIN
+        } else if raw > Self::MAX.value {
+            Self::MAX
+        } else {
+            Self { value: raw }
         }
     }
 
-    pub fn min_value() -> Self {
-        Self {
-            value: Self::MIN_PRIO,
-        }
-    }
-
-    pub fn raw_val(&self) -> i32 {
+    /// Convert to the raw value with range [19, -20].
+    pub fn to_raw_val(self) -> i8 {
         self.value
     }
-
-    /// Convert [19,-20] to priority value [39,0].
-    pub fn to_priority_val(&self) -> i32 {
-        self.value - Self::MIN_PRIO
-    }
-
-    /// Convert [19,-20] to rlimit style value [1,40].
-    pub fn to_rlimit_val(&self) -> i32 {
-        Self::MAX_PRIO - self.value + 1
-    }
 }
 
 impl From<i32> for NiceValue {
     fn from(raw: i32) -> Self {
-        let value = if raw < Self::MIN_PRIO {
-            Self::MIN_PRIO
-        } else if raw > Self::MAX_PRIO {
-            Self::MAX_PRIO
+        let adj_raw = if raw > i8::MAX as i32 {
+            i8::MAX
+        } else if raw < i8::MIN as i32 {
+            i8::MIN
         } else {
-            raw
+            raw as i8
         };
-        Self { value }
+        Self::new(adj_raw)
     }
 }

src/libos/src/sched/syscalls.rs

@@ -83,16 +83,16 @@ pub fn do_getcpu(cpu_ptr: *mut u32, node_ptr: *mut u32) -> Result<isize> {
 
 pub fn do_set_priority(which: i32, who: i32, prio: i32) -> Result<isize> {
     let which = PrioWhich::try_from(which)?;
-    let prio = NiceValue::from(prio);
-    super::do_priority::do_set_priority(which, who, prio)?;
+    let nice = NiceValue::from(prio);
+    super::do_priority::do_set_priority(which, who, nice)?;
     Ok(0)
 }
 
 pub fn do_get_priority(which: i32, who: i32) -> Result<isize> {
     let which = PrioWhich::try_from(which)?;
-    let prio = super::do_priority::do_get_priority(which, who)?;
+    let nice = super::do_priority::do_get_priority(which, who)?;
     // To avoid negative return values, "getpriority()" will
     // not return the normal nice-value, but a negated value that
     // has been offset by 20 (ie it returns 40..1 instead of -20..19)
-    Ok(prio.to_rlimit_val() as isize)
+    Ok((20 - nice.to_raw_val()) as _)
 }