Add additional counter for syscall switches.

src/context/mod.rs

@@ -386,11 +386,12 @@ impl Drop for PreemptGuardL2<'_> {
     }
 }
 
-pub fn get_contexts_stats(token: &mut CleanLockToken) -> (usize, usize, usize, usize) {
+pub fn get_contexts_stats(token: &mut CleanLockToken) -> [usize; 5] {
     let alive = contexts(token.downgrade()).len();
 
     let mut running = 0;
     let mut switches = 0;
+    let mut syscall_switches = 0;
 
     for i in 0..crate::cpu_count() {
         if let Some(percpu) = unsafe {
@@ -399,11 +400,13 @@ pub fn get_contexts_stats(token: &mut CleanLockToken) -> (usize, usize, usize, u
                 .as_ref()
         } {
             running += percpu.switch_internals.run_queue.lock().queue.len();
-            switches += CpuStatsData::from(&percpu.stats).context_switches as usize;
+            let data = CpuStatsData::from(&percpu.stats);
+            switches += data.context_switches as usize;
+            syscall_switches += data.syscall_switches as usize;
         }
     }
 
     let blocked = alive.saturating_sub(running);
 
-    (alive, running, blocked, switches)
+    [alive, running, blocked, switches, syscall_switches]
 }

src/context/switch.rs

@@ -180,7 +180,7 @@ pub fn switch(token: &mut CleanLockToken) -> SwitchResult {
     let switch_time = crate::time::monotonic(token);
 
     let percpu = PercpuBlock::current();
-    percpu.stats.add_context_switch();
+    percpu.stats.add_context_switch(percpu.inside_syscall.get());
 
     //set PIT Interrupt counter to 0, giving each process same amount of PIT ticks
     percpu.switch_internals.pit_ticks.set(0);

src/cpu_stats.rs

@@ -39,8 +39,10 @@ pub struct CpuStats {
     irq: AtomicU64,
     /// Current state of the CPU
     state: AtomicU8,
-    /// The number of times (overall) where a CPU switched from one context to another.
+    /// The number of times this CPU switched from one context to another.
     context_switches: AtomicU64,
+    /// The number of times this CPU switched while handling a syscall.
+    syscall_switches: AtomicU64,
 }
 
 impl CpuStats {
@@ -53,6 +55,7 @@ impl CpuStats {
             irq: AtomicU64::new(0),
             state: AtomicU8::new(0),
             context_switches: AtomicU64::new(0),
+            syscall_switches: AtomicU64::new(0),
         }
     }
 }
@@ -70,6 +73,8 @@ pub struct CpuStatsData {
     pub irq: u64,
     /// Number of context switches on this CPU
     pub context_switches: u64,
+    /// Number of syscall-caused context switches on this CPU
+    pub syscall_switches: u64,
 }
 
 impl CpuStats {
@@ -118,12 +123,18 @@ impl CpuStats {
 
     /// Add a context switch to the count.
     #[inline]
-    pub fn add_context_switch(&self) {
+    pub fn add_context_switch(&self, inside_syscall: bool) {
         // Again this is percpu, so fetch_add is unnecessary.
         self.context_switches.store(
             self.context_switches.load(Ordering::Relaxed) + 1,
             Ordering::Relaxed,
         );
+        if inside_syscall {
+            self.syscall_switches.store(
+                self.syscall_switches.load(Ordering::Relaxed) + 1,
+                Ordering::Relaxed,
+            );
+        }
     }
 }
 
@@ -146,6 +157,7 @@ impl From<&CpuStats> for CpuStatsData {
             idle: val.idle.load(Ordering::Relaxed),
             irq: val.irq.load(Ordering::Relaxed),
             context_switches: val.context_switches.load(Ordering::Relaxed),
+            syscall_switches: val.syscall_switches.load(Ordering::Relaxed),
         }
     }
 }

src/scheme/sys/stat.rs

@@ -15,7 +15,7 @@ use alloc::{string::String, vec::Vec};
 pub fn resource(token: &mut CleanLockToken) -> Result<Vec<u8>> {
     let start_time_sec = *START.lock(token.token()) / 1_000_000_000;
 
-    let (contexts_alive, contexts_running, contexts_blocked, context_switches) =
+    let [contexts_alive, contexts_running, contexts_blocked, context_switches, syscall_switches] =
         get_contexts_stats(token);
     let (event_keys, event_subs) = get_event_stat(token);
     let (futex_keys, futex_subs) = get_futex_stat(token);
@@ -25,6 +25,7 @@ pub fn resource(token: &mut CleanLockToken) -> Result<Vec<u8>> {
         "{}{}\n\
         boot_time: {start_time_sec}\n\
         context_switches: {}\n\
+        syscall_switches: {}\n\
         contexts_created: {}\n\
         contexts_alive: {contexts_alive}\n\
         contexts_running: {contexts_running}\n\
@@ -38,6 +39,7 @@ pub fn resource(token: &mut CleanLockToken) -> Result<Vec<u8>> {
         get_cpu_stats(),
         get_irq_stats(),
         context_switches,
+        syscall_switches,
         get_contexts_count(),
     );