sharedcache: reduce the scope of TestSharedCacheRandomized under race

Reduce the max number of shards and skip the random block size tests
under race. This significantly reduces the runtime and memory
footprint of the test.

Informs: #2741

objstorage/objstorageprovider/sharedcache/shared_cache_test.go

@@ -11,6 +11,7 @@ import (
 
 	"github.com/cockroachdb/datadriven"
 	"github.com/cockroachdb/pebble/internal/base"
+	"github.com/cockroachdb/pebble/internal/invariants"
 	"github.com/cockroachdb/pebble/objstorage"
 	"github.com/cockroachdb/pebble/objstorage/objstorageprovider"
 	"github.com/cockroachdb/pebble/objstorage/objstorageprovider/sharedcache"
@@ -135,7 +136,11 @@ func TestSharedCacheRandomized(t *testing.T) {
 		return func(t *testing.T) {
 			for _, concurrentReads := range []bool{false, true} {
 				t.Run(fmt.Sprintf("concurrentReads=%v", concurrentReads), func(t *testing.T) {
-					numShards := rand.Intn(64) + 1
+					maxShards := 64
+					if invariants.RaceEnabled {
+						maxShards = 8
+					}
+					numShards := rand.Intn(maxShards) + 1
 					cacheSize := shardingBlockSize * int64(numShards) // minimum allowed cache size
 
 					cache, err := sharedcache.Open(fs, base.DefaultLogger, "", blockSize, shardingBlockSize, cacheSize, numShards)
@@ -195,14 +200,16 @@ func TestSharedCacheRandomized(t *testing.T) {
 	t.Run("32 KB block size", helper(32*1024, 1024*1024))
 	t.Run("1 MB block size", helper(1024*1024, 1024*1024))
 
-	for i := 0; i < 5; i++ {
-		exp := rand.Intn(11) + 10   // [10, 20]
-		randomBlockSize := 1 << exp // [1 KB, 1 MB]
+	if !invariants.RaceEnabled {
+		for i := 0; i < 5; i++ {
+			exp := rand.Intn(11) + 10   // [10, 20]
+			randomBlockSize := 1 << exp // [1 KB, 1 MB]
 
-		factor := rand.Intn(10) + 1                                // [1, 10]
-		randomShardingBlockSize := int64(randomBlockSize * factor) // [1 KB, 10 MB]
+			factor := rand.Intn(10) + 1                                // [1, 10]
+			randomShardingBlockSize := int64(randomBlockSize * factor) // [1 KB, 10 MB]
 
-		t.Run("random block and sharding block size", helper(randomBlockSize, randomShardingBlockSize))
+			t.Run("random block and sharding block size", helper(randomBlockSize, randomShardingBlockSize))
+		}
 	}
 }