feat: charge event gas

This charges the correct event gas and adds a few benchmarks. It also:

1. Tries to remove some variability when recording events by
pre-allocating space.`
2. Validates utf8 up-front, then slices the validated string for better
performance (and easier benchmarking).

fvm/src/call_manager/default.rs

@@ -901,11 +901,18 @@ where
 /// If an actor aborts, the last layer should be discarded (discard_last_layer). This will also
 /// throw away any events collected from subcalls (and previously merged, as those subcalls returned
 /// normally).
-#[derive(Default)]
 pub struct EventsAccumulator {
     events: Vec<StampedEvent>,
     idxs: Vec<usize>,
 }
+impl Default for EventsAccumulator {
+    fn default() -> Self {
+        Self {
+            events: Vec::with_capacity(128),
+            idxs: Vec::with_capacity(8),
+        }
+    }
+}
 
 pub(crate) struct Events {
     root: Option<Cid>,

fvm/src/gas/price_list.rs

@@ -312,14 +312,14 @@ lazy_static! {
         // TODO(#1817): Per-entry event validation cost. These parameters were benchmarked for the
         // EVM but haven't been revisited since revising the API.
         event_per_entry: ScalingCost {
-            flat: Gas::new(1750),
-            scale: Gas::new(25),
+            flat: Gas::new(2000),
+            scale: Gas::new(1400),
         },
 
         // TODO(#1817): Cost of validating utf8 (used in event parsing).
         utf8_validation: ScalingCost {
-            flat: Zero::zero(),
-            scale: Zero::zero(),
+            flat: Gas::new(500),
+            scale: Gas::new(16),
         },
 
         // Preloaded actor IDs per FIP-0055.
@@ -627,6 +627,15 @@ impl PriceList {
         GasCharge::new("OnHashing", gas, Zero::zero())
     }
 
+    #[inline]
+    pub fn on_utf8_validation(&self, len: usize) -> GasCharge {
+        GasCharge::new(
+            "OnUtf8Validation",
+            self.utf8_validation.apply(len),
+            Zero::zero(),
+        )
+    }
+
     /// Returns gas required for computing unsealed sector Cid.
     #[inline]
     pub fn on_compute_unsealed_sector_cid(
@@ -966,11 +975,11 @@ impl PriceList {
 
         GasCharge::new(
             "OnActorEvent",
-            // Charge for validation/storing events.
-            mem + validate_entries + validate_utf8,
+            // Charge for validation/storing/serializing events.
+            mem * 2u32 + validate_entries + validate_utf8,
             // Charge for forming the AMT and returning the events to the client.
             // one copy into the AMT, one copy to the client.
-            hash + (mem * 2u32),
+            hash + mem,
         )
     }
 

fvm/src/kernel/default.rs

@@ -1061,6 +1061,11 @@ where
             return Err(syscall_error!(IllegalArgument; "total event value lengths exceeded the max size: {} > {MAX_TOTAL_VALUES_LEN}", event_values.len()).into());
         }
 
+        // We validate utf8 all at once for better performance.
+        let event_keys = std::str::from_utf8(event_keys)
+            .context("invalid event key")
+            .or_illegal_argument()?;
+
         let mut key_offset: usize = 0;
         let mut val_offset: usize = 0;
 
@@ -1098,10 +1103,6 @@ where
                 .context("event entry key out of range")
                 .or_illegal_argument()?;
 
-            let key = std::str::from_utf8(key)
-                .context("invalid event key")
-                .or_illegal_argument()?;
-
             let value = &event_values
                 .get(val_offset..val_offset + header.val_len as usize)
                 .context("event entry value out of range")
@@ -1125,6 +1126,10 @@ where
         let actor_evt = ActorEvent::from(entries);
 
         let stamped_evt = StampedEvent::new(self.actor_id, actor_evt);
+        // Enable this when performing gas calibration to measure the cost of serializing early.
+        #[cfg(feature = "gas_calibration")]
+        let _ = fvm_ipld_encoding::to_vec(&stamped_evt).unwrap();
+
         self.call_manager.append_event(stamped_evt);
 
         t.stop();

testing/calibration/shared/src/lib.rs

@@ -19,7 +19,7 @@ pub enum Method {
     OnRecoverSecpPublicKey,
     /// Measure sends
     OnSend,
-    /// Emit events, driven by the selected mode. See EventCalibrationMode for more info.
+    /// Emit events
     OnEvent,
     /// Read/write blocks with different numbers of CBOR fields & links.
     OnScanIpldLinks,
@@ -64,18 +64,11 @@ pub struct OnRecoverSecpPublicKeyParams {
     pub seed: u64,
 }
 
-#[derive(Serialize, Deserialize)]
-pub enum EventCalibrationMode {
-    /// Produce events with the specified shape.
-    Shape((usize, usize, usize)),
-    /// Attempt to reach a target size for the CBOR event.
-    TargetSize(usize),
-}
-
 #[derive(Serialize, Deserialize)]
 pub struct OnEventParams {
     pub iterations: usize,
-    pub mode: EventCalibrationMode,
+    // Total size of the values.
+    pub total_value_size: usize,
     /// Number of entries in the event.
     pub entries: usize,
     /// Flags to apply to all entries.

testing/integration/Cargo.toml

@@ -41,8 +41,9 @@ serde_json = "1.0"
 bls-signatures = { version = "0.13", default-features = false }
 wat = "1.0.66"
 hex = "0.4.3"
+minstant = "0.1.3"
 
 [features]
 default = []
 m2-native = []
-calibration = []
+calibration = ["fvm/gas_calibration"]