From 91176e4b245075e1f0bb23b9aeb3f1132c5e29ae Mon Sep 17 00:00:00 2001
From: Emmanuel T Odeke <emmanuel@orijtech.com>
Date: Sat, 28 Dec 2024 15:26:02 -0800
Subject: [PATCH] perf(gnovm): cache PkgIDFromPkgPath for higher performance
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This change comes from noticing that PkgIDFromPkgPath is very
heavily invoked within the VM yet its results with the same inputs
produced deterministic results aka SHA256(path)[:20]
Previously just spinning up the VM would take 80 seconds, with this
change that's shaved by ~8-10 seconds down and with repeatable and
visible results exhibited through:

- Benchmark:

```shell
$ benchstat before.txt after.txt
name                old time/op    new time/op    delta
PkgIDFromPkgPath-8    1.96µs ± 2%    0.35µs ± 1%  -82.40%  (p=0.000 n=20+18)

name                old alloc/op   new alloc/op   delta
PkgIDFromPkgPath-8      296B ± 0%      168B ± 0%  -43.24%  (p=0.000 n=20+20)

name                old allocs/op  new allocs/op  delta
PkgIDFromPkgPath-8      9.00 ± 0%      7.00 ± 0%  -22.22%  (p=0.000 n=20+20)
```

- Profiles:

* Before
```shell
(pprof) list PkgIDFromPkgPath
Total: 100.94s
ROUTINE ======================== github.com/gnolang/gno/gnovm/pkg/gnolang.PkgIDFromPkgPath in $PATH
     220ms      9.26s (flat, cum)  9.17% of Total
         .          .     74:func PkgIDFromPkgPath(path string) PkgID {
     220ms      9.26s     75:	return PkgID{HashBytes([]byte(path))}
         .          .     76:}
         .          .     77:
         .          .     78:// Returns the ObjectID of the PackageValue associated with path.
         .          .     79:func ObjectIDFromPkgPath(path string) ObjectID {
         .          .     80:	pkgID := PkgIDFromPkgPath(path)
```

* After
```shell
(pprof) list PkgIDFromPkgPath
Total: 93.22s
ROUTINE ======================== github.com/gnolang/gno/gnovm/pkg/gnolang.PkgIDFromPkgPath in $PATH
     210ms      1.55s (flat, cum)  1.66% of Total
      50ms       50ms     78:func PkgIDFromPkgPath(path string) PkgID {
         .      490ms     79:	pkgIDMu.Lock()
      10ms       10ms     80:	defer pkgIDMu.Unlock()
         .          .     81:
      10ms      730ms     82:	pkgID, ok := pkgIDFromPkgPathCache[path]
         .          .     83:	if !ok {
         .          .     84:		pkgID = new(PkgID)
         .          .     85:		*pkgID = PkgID{HashBytes([]byte(path))}
         .          .     86:		pkgIDFromPkgPathCache[path] = pkgID
         .          .     87:	}
     140ms      270ms     88:	return *pkgID
         .          .     89:}
         .          .     90:
         .          .     91:// Returns the ObjectID of the PackageValue associated with path.
         .          .     92:func ObjectIDFromPkgPath(path string) ObjectID {
         .          .     93:	pkgID := PkgIDFromPkgPath(path)
```

Fixes #3423
---
 gnovm/pkg/gnolang/bench_test.go | 31 +++++++++++++++++++++++++++++++
 gnovm/pkg/gnolang/realm.go      | 20 +++++++++++++++++++-
 2 files changed, 50 insertions(+), 1 deletion(-)
 create mode 100644 gnovm/pkg/gnolang/bench_test.go

diff --git a/gnovm/pkg/gnolang/bench_test.go b/gnovm/pkg/gnolang/bench_test.go
new file mode 100644
index 00000000000..b638ab66cd0
--- /dev/null
+++ b/gnovm/pkg/gnolang/bench_test.go
@@ -0,0 +1,31 @@
+package gnolang
+
+import (
+	"testing"
+)
+
+var sink any = nil
+
+var pkgIDPaths = []string{
+	"encoding/json",
+	"math/bits",
+	"github.com/gnolang/gno/gnovm/pkg/gnolang",
+	"a",
+	" ",
+	"",
+	"github.com/gnolang/gno/gnovm/pkg/gnolang/vendor/pkg/github.com/gnolang/vendored",
+}
+
+func BenchmarkPkgIDFromPkgPath(b *testing.B) {
+	b.ReportAllocs()
+	for i := 0; i < b.N; i++ {
+		for _, path := range pkgIDPaths {
+			sink = PkgIDFromPkgPath(path)
+		}
+	}
+
+	if sink == nil {
+		b.Fatal("Benchmark did not run!")
+	}
+	sink = nil
+}
diff --git a/gnovm/pkg/gnolang/realm.go b/gnovm/pkg/gnolang/realm.go
index d822eb290eb..4100d9dace8 100644
--- a/gnovm/pkg/gnolang/realm.go
+++ b/gnovm/pkg/gnolang/realm.go
@@ -6,6 +6,7 @@ import (
 	"fmt"
 	"reflect"
 	"strings"
+	"sync"
 
 	bm "github.com/gnolang/gno/gnovm/pkg/benchops"
 )
@@ -71,8 +72,25 @@ func (pid PkgID) Bytes() []byte {
 	return pid.Hashlet[:]
 }
 
+var (
+	pkgIDMu sync.Mutex // pkgIDMu protects the shared cache.
+	// TODO: later on switch this to an LRU if needed to ensure
+	// fixed memory caps. For now though it isn't a problem:
+	// https://github.com/gnolang/gno/pull/3424#issuecomment-2564571785
+	pkgIDFromPkgPathCache = make(map[string]*PkgID, 100)
+)
+
 func PkgIDFromPkgPath(path string) PkgID {
-	return PkgID{HashBytes([]byte(path))}
+	pkgIDMu.Lock()
+	defer pkgIDMu.Unlock()
+
+	pkgID, ok := pkgIDFromPkgPathCache[path]
+	if !ok {
+		pkgID = new(PkgID)
+		*pkgID = PkgID{HashBytes([]byte(path))}
+		pkgIDFromPkgPathCache[path] = pkgID
+	}
+	return *pkgID
 }
 
 // Returns the ObjectID of the PackageValue associated with path.