use one bit instead of vec

dfir_rs/src/scheduled/context.rs

@@ -3,14 +3,13 @@
 //! Provides APIs for state and scheduling.
 
 use std::any::Any;
-use std::cell::RefCell;
+use std::cell::Cell;
 use std::collections::VecDeque;
 use std::future::Future;
 use std::marker::PhantomData;
 use std::ops::DerefMut;
 use std::pin::Pin;
 
-use smallvec::SmallVec;
 use tokio::sync::mpsc::{self, UnboundedReceiver, UnboundedSender};
 use tokio::task::JoinHandle;
 use web_time::SystemTime;
@@ -42,8 +41,8 @@ pub struct Context {
     /// Second field (bool) is for if the event is an external "important" event (true).
     pub(super) event_queue_send: UnboundedSender<(SubgraphId, bool)>,
 
-    /// Subgraphs rescheduled in the current stratum.
-    pub(super) rescheduled_subgraphs: RefCell<SmallVec<[SubgraphId; 1]>>,
+    /// If the current subgraph wants to reschedule in the current tick+stratum.
+    pub(super) reschedule_current_subgraph: Cell<bool>,
 
     pub(super) current_tick: TickInstant,
     pub(super) current_stratum: usize,
@@ -100,9 +99,7 @@ impl Context {
 
     /// Schedules the current subgraph to run again _this tick_.
     pub fn reschedule_current_subgraph(&self) {
-        self.rescheduled_subgraphs
-            .borrow_mut()
-            .push(self.subgraph_id);
+        self.reschedule_current_subgraph.set(true);
     }
 
     /// Returns a `Waker` for interacting with async Rust.
@@ -246,7 +243,7 @@ impl Default for Context {
             events_received_tick: false,
 
             event_queue_send,
-            rescheduled_subgraphs: Default::default(),
+            reschedule_current_subgraph: Cell::new(false),
 
             current_stratum: 0,
             current_tick: TickInstant::default(),

dfir_rs/src/scheduled/graph.rs

@@ -282,6 +282,7 @@ impl<'a> Dfir<'a> {
             }
 
             let sg_data = &self.subgraphs[sg_id.0];
+            debug_assert_eq!(self.context.current_stratum, sg_data.stratum);
             for &handoff_id in sg_data.succs.iter() {
                 let handoff = &self.handoffs[handoff_id.0];
                 if !handoff.handoff.is_bottom() {
@@ -299,9 +300,9 @@ impl<'a> Dfir<'a> {
                 }
             }
 
-            for sg_id in self.context.rescheduled_subgraphs.borrow_mut().drain(..) {
-                let sg_data = &self.subgraphs[sg_id.0];
-                assert_eq!(sg_data.stratum, self.context.current_stratum);
+            // Check if subgraph wants rescheduling
+            if self.context.reschedule_current_subgraph.take() {
+                // Add subgraph to stratum queue if it is not already scheduled.
                 if !sg_data.is_scheduled.replace(true) {
                     self.context.stratum_queues[sg_data.stratum].push_back(sg_id);
                 }