From 04b2c4631d3a832591afe6c647839ad7a24aa2bd Mon Sep 17 00:00:00 2001
From: Jamie Liu <jamieliu@google.com>
Date: Thu, 15 Aug 2024 16:26:48 -0700
Subject: [PATCH] state: fix redundant reconciliation in
 typeDecodeDatabase.Lookup()

Simple microbenchmark for save+load of a pgalloc.memAcctSet:
Before this CL:

```
goos: linux
goarch: amd64
pkg: pkg/sentry/pgalloc/pgalloc
cpu: Intel(R) Xeon(R) CPU @ 2.60GHz
BenchmarkMemAcctSetSaveLoad
BenchmarkMemAcctSetSaveLoad/1000
BenchmarkMemAcctSetSaveLoad/1000-48                  362           3313192 ns/op
BenchmarkMemAcctSetSaveLoad/10000
BenchmarkMemAcctSetSaveLoad/10000-48                  33          35237918 ns/op
BenchmarkMemAcctSetSaveLoad/100000
BenchmarkMemAcctSetSaveLoad/100000-48                  3         360797304 ns/op
PASS
```

After this CL:

```
goos: linux
goarch: amd64
pkg: pkg/sentry/pgalloc/pgalloc
cpu: Intel(R) Xeon(R) CPU @ 2.60GHz
BenchmarkMemAcctSetSaveLoad
BenchmarkMemAcctSetSaveLoad/1000
BenchmarkMemAcctSetSaveLoad/1000-48                  417           2837200 ns/op
BenchmarkMemAcctSetSaveLoad/10000
BenchmarkMemAcctSetSaveLoad/10000-48                  38          30813388 ns/op
BenchmarkMemAcctSetSaveLoad/100000
BenchmarkMemAcctSetSaveLoad/100000-48                  4         311275972 ns/op
PASS
```
PiperOrigin-RevId: 663494805
---
 pkg/state/types.go | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/pkg/state/types.go b/pkg/state/types.go
index d3e1cbfe3..09f889084 100644
--- a/pkg/state/types.go
+++ b/pkg/state/types.go
@@ -204,7 +204,7 @@ var singleFieldOrder = []int{0}
 //
 // This method never returns nil.
 func (tbd *typeDecodeDatabase) Lookup(id typeID, typ reflect.Type) *reconciledTypeEntry {
-	if len(tbd.byID) > int(id) && tbd.byID[id-1] != nil {
+	if len(tbd.byID) >= int(id) && tbd.byID[id-1] != nil {
 		// Already reconciled.
 		return tbd.byID[id-1]
 	}