chore: fvm: update FFI to not arbitrary limit FVM concurrency

CHANGELOG.md

@@ -34,6 +34,16 @@ There is no change in the behaviour when a call returns an error, as the error o
 
 ## New features
 
+### FVM RPC Concurrent Requests
+
+The default maximum FVM concurrency (`LOTUS_FVM_CONCURRENCY`) has increased from 4 to the number of available CPU threads. Furthermore, the FVM now allocates `LOTUS_FVM_CONCURRENCY` OS-level threads with 64MiB stacks (in 1.26, we allocated one thread per CPU core regardless of the value of `LOTUS_FVM_CONCURRENCY`).
+
+Impact:
+
+1. This will increase memory usage for nodes specifying a higher `LOTUS_FVM_CONCURRENCY` than the number of CPU threads they have available.
+2. This will allow such nodes to actually take advantage of this higher concurrency limit where the concurrency was previously capped at the number of available CPU threads.
+
+
 ## Improvements
 
 # v1.27.0 / 2024-05-27

chain/vm/execution.go

@@ -3,6 +3,7 @@ package vm
 import (
 	"context"
 	"os"
+	"runtime"
 	"strconv"
 	"sync"
 
@@ -14,16 +15,15 @@ import (
 	"github.com/filecoin-project/lotus/metrics"
 )
 
-const (
-	// DefaultAvailableExecutionLanes is the number of available execution lanes; it is the bound of
-	// concurrent active executions.
-	// This is the default value in filecoin-ffi
-	DefaultAvailableExecutionLanes = 4
-	// DefaultPriorityExecutionLanes is the number of reserved execution lanes for priority computations.
-	// This is purely userspace, but we believe it is a reasonable default, even with more available
-	// lanes.
-	DefaultPriorityExecutionLanes = 2
-)
+// DefaultPriorityExecutionLanes is the number of reserved execution lanes for priority computations.
+// This is purely userspace, but we believe it is a reasonable default, even with more available
+// lanes.
+const DefaultPriorityExecutionLanes = 2
+
+// DefaultAvailableExecutionLanes is the number of available execution lanes; it is the bound of
+// concurrent active executions.
+// This is the default value in filecoin-ffi
+var DefaultAvailableExecutionLanes = runtime.NumCPU()
 
 // the execution environment; see below for definition, methods, and initialization
 var execution *executionEnv

node/modules/alerts.go

@@ -117,13 +117,20 @@ func CheckFvmConcurrency() func(al *alerting.Alerting) {
 			return
 		}
 
-		// Raise alert if LOTUS_FVM_CONCURRENCY is set to a high value
-		if fvmConcurrencyVal > 24 {
+		if fvmConcurrencyVal < 2 {
 			alert := al.AddAlertType("process", "fvm-concurrency")
 			al.Raise(alert, map[string]interface{}{
-				"message":     "LOTUS_FVM_CONCURRENCY is set to a high value that can cause chain sync panics on network migrations/upgrades",
+				"message":     "LOTUS_FVM_CONCURRENCY should be at least 2",
 				"set_value":   fvmConcurrencyVal,
-				"recommended": "24 or less during network upgrades",
+				"recommended": "set it to two or more",
+			})
+		}
+		if fvmConcurrencyVal > 512 {
+			alert := al.AddAlertType("process", "fvm-concurrency")
+			al.Raise(alert, map[string]interface{}{
+				"message":     "LOTUS_FVM_CONCURRENCY is set to a high value that can cause chain sync panics on network migrations/upgrades and excessive memory usage (>32GiB)",
+				"set_value":   fvmConcurrencyVal,
+				"recommended": "leave it unset to default to the number of available cpu threads",
 			})
 		}
 	}