[analyzer] Introduce --disable-file-byte-store

Intended for benchmarking in combination with `--train-using` to make
the instruction count used more stable.

E.g. run like

```
perf stat -e "instructions:u" \
  out/ReleaseX64/dart-sdk/bin/dartaotruntime \
  --deterministic pkg/analysis_server/bin/server.aot \
  --disable-file-byte-store --train-using pkg/front_end/lib/
```

(on an aot-compiled server (

```
out/ReleaseX64/dart-sdk/bin/dart compile \
  aot-snapshot pkg/analysis_server/bin/server.dart`
```

)

looking at `instructions:u` the standard deviation is reduced quite a
bit compared to not passing the new parameter.

Without: 179,111,320 (95% becomes ±0.14%)
With: 2,743,207 (95% becomes ±0.002%)

Raw (although sorsted) numbers:

Without:

```
51,029,580,408
51,032,748,835
51,033,471,737
51,040,240,638
51,041,785,525
51,042,264,608
51,059,291,236
51,102,379,269
51,112,553,122
51,130,806,654
51,132,553,799
51,136,189,490
51,145,979,715
51,154,797,225
51,157,949,300
51,158,330,761
51,158,991,218
51,166,545,840
51,173,629,326
51,291,270,598
51,457,570,261
51,460,114,586
51,475,491,602
51,545,172,493
51,658,750,242
```

With:

```
49,878,337,415
49,878,419,595
49,879,001,051
49,881,016,075
49,882,607,217
49,882,624,488
49,883,029,234
49,883,305,881
49,883,384,825
49,883,585,095
49,883,725,866
49,884,020,490
49,884,020,988
49,884,213,971
49,884,552,882
49,884,562,548
49,884,644,369
49,885,275,225
49,885,344,007
49,885,914,848
49,886,165,117
49,886,968,388
49,887,615,329
49,888,309,000
49,888,930,570
```

Change-Id: Id492e094a3176c2877f15e5952767ea55bef3657
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/428000
Commit-Queue: Jens Johansen <[email protected]>
Reviewed-by: Brian Wilkerson <[email protected]>

Author: jensjoha

pkg/analysis_server/lib/src/analysis_server.dart

@@ -570,6 +570,10 @@ abstract class AnalysisServer {
       return providedByteStore;
     }
 
+    if (options.disableFileByteStore ?? false) {
+      return MemoryCachingByteStore(NullByteStore(), memoryCacheSize);
+    }
+
     if (resourceProvider is OverlayResourceProvider) {
       resourceProvider = resourceProvider.baseProvider;
     }

pkg/analysis_server/lib/src/legacy_analysis_server.dart

@@ -142,6 +142,12 @@ class AnalysisServerOptions {
   /// Base path where to cache data.
   String? cacheFolder;
 
+  /// If [true] don't create a (Evicting)FileByteStore.
+  ///
+  /// Intended for benchmarking as it makes "instructions:u" in `perf stat` more
+  /// stable, although it then doesn't benchmark that code.
+  bool? disableFileByteStore;
+
   /// The path to the package config file override.
   /// If `null`, then the default discovery mechanism is used.
   String? packagesFile;

pkg/analysis_server/lib/src/server/driver.dart

@@ -133,6 +133,9 @@ class Driver implements ServerStarter {
   /// A directory to analyze in order to train an analysis server snapshot.
   static const String TRAIN_USING = 'train-using';
 
+  /// Flag to not use a (Evicting)FileByteStore.
+  static const String DISABLE_FILE_BYTE_STORE = 'disable-file-byte-store';
+
   /// The builder for attachments that should be included into crash reports.
   CrashReportingAttachmentsBuilder crashReportingAttachmentsBuilder =
       CrashReportingAttachmentsBuilder.empty;
@@ -421,6 +424,9 @@ class Driver implements ServerStarter {
         'analysis_server_',
       );
       analysisServerOptions.cacheFolder = tempDriverDir.path;
+      analysisServerOptions.disableFileByteStore = results.flag(
+        DISABLE_FILE_BYTE_STORE,
+      );
 
       var devServer = DevAnalysisServer(socketServer);
       devServer.initServer();
@@ -650,6 +656,7 @@ class Driver implements ServerStarter {
       USE_LSP,
       'use-new-relevance',
       'use-fasta-parser',
+      DISABLE_FILE_BYTE_STORE,
     ];
     return knownArguments
         .where((argument) => results.wasParsed(argument))
@@ -842,6 +849,12 @@ class Driver implements ServerStarter {
           'analysis server snapshot.  Disables analytics.',
       hide: true,
     );
+    parser.addFlag(
+      DISABLE_FILE_BYTE_STORE,
+      help:
+          'Disable use of (Evicting)FileByteStore. Intended for benchmarking.',
+      hide: true,
+    );
     parser.addFlag(
       DISABLE_SERVER_EXCEPTION_HANDLING,
       // TODO(jcollins-g): Pipeline option through and apply to all