ChrisHegarty commented on code in PR #13196:
URL: https://github.com/apache/lucene/pull/13196#discussion_r1534598790
##########
lucene/core/src/java21/org/apache/lucene/store/MemorySegmentIndexInputProvider.java:
##########
@@ -92,10 +110,19 @@ private final MemorySegment[] map(
}
if (preload) {
segment.load();
+ } else if (segSize > 0L && advice.isPresent()) { // not when preloading!
+ nativeAccess.madvise(segment, advice.getAsInt());
}
segments[segNr] = segment;
startOffset += segSize;
}
return segments;
}
+
+ private OptionalInt mapContextToMadvise(IOContext context) {
+ if (context.readOnce || context.context == Context.MERGE) {
+ return OptionalInt.of(NativeAccess.POSIX_MADV_SEQUENTIAL);
+ }
Review Comment:
I'd like to plumb `POSIX_MADV_RANDOM`, for use when reading from flat vector
data. Any objection do doing it in this PR, or you wanna wait to get this in
first?
##########
lucene/core/src/java21/org/apache/lucene/store/PosixNativeAccess.java:
##########
@@ -0,0 +1,82 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.lucene.store;
+
+import java.io.IOException;
+import java.lang.foreign.FunctionDescriptor;
+import java.lang.foreign.Linker;
+import java.lang.foreign.MemorySegment;
+import java.lang.foreign.SymbolLookup;
+import java.lang.foreign.ValueLayout;
+import java.lang.invoke.MethodHandle;
+import java.util.Locale;
+import java.util.logging.Logger;
+
+@SuppressWarnings("preview")
+final class PosixNativeAccess extends NativeAccess {
+
+ private static final Logger LOG =
Logger.getLogger(PosixNativeAccess.class.getName());
+
+ private final MethodHandle mh$posix_madvise;
Review Comment:
we should probably make this MethodHandle `static final`. In which case the
whole instance construction can be cleaned up a bit.
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