Implement benchmark for looking up FileStore of a given Path

Results on Mac OS 10.14.6 using APFS:

Result "org.eclipse.jgit.benchmarks.LookupFileStoreBenchmark.testLookupFileStore":
  44583.277 ±(99.9%) 2666.096 ns/op [Average]
  (min, avg, max) = (43707.073, 44583.277, 45320.685), stdev = 692.377
  CI (99.9%): [41917.181, 47249.373] (assumes normal distribution)

Secondary result
"org.eclipse.jgit.benchmarks.LookupFileStoreBenchmark.testLookupFileStore:·stack":
Stack profiler:

....[Thread state
distributions]........................................................
100.0%         RUNNABLE

....[Thread state:
RUNNABLE].............................................................
 42.5%  42.5% sun.nio.fs.UnixNativeDispatcher.realpath0
 37.9%  37.9% sun.nio.fs.UnixNativeDispatcher.stat0
 11.0%  11.0% sun.nio.fs.BsdNativeDispatcher.getfsstat
  7.6%   7.6% sun.nio.fs.BsdNativeDispatcher.fsstatEntry
  0.7%   0.7% sun.nio.fs.BsdNativeDispatcher.endfsstat
  0.1%   0.1% sun.nio.fs.UnixPath.initOffsets
  0.0%   0.0% sun.nio.fs.UnixFileAttributes.get
  0.0%   0.0% java.util.zip.Inflater.inflateBytes
  0.0%   0.0% sun.misc.Unsafe.compareAndSwapInt
  0.0%   0.0% sun.nio.fs.BsdFileStore.findMountEntry

This shows that FS.attrCacheByPath should be useful to reduce overhead
of looking up the FileStore of a given file.

Change-Id: I7213086b42e0453f0ee149660d507dac2a4644cc
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>

org.eclipse.jgit.benchmarks/src/org/eclipse/jgit/benchmarks/LookupFileStoreBenchmark.java

@@ -0,0 +1,97 @@
+/*
+ * Copyright (C) 2019, Matthias Sohn <matthias.sohn@sap.com>
+ * and other copyright owners as documented in the project's IP log.
+ *
+ * This program and the accompanying materials are made available
+ * under the terms of the Eclipse Distribution License v1.0 which
+ * accompanies this distribution, is reproduced below, and is
+ * available at http://www.eclipse.org/org/documents/edl-v10.php
+ *
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or
+ * without modification, are permitted provided that the following
+ * conditions are met:
+ *
+ * - Redistributions of source code must retain the above copyright
+ *   notice, this list of conditions and the following disclaimer.
+ *
+ * - Redistributions in binary form must reproduce the above
+ *   copyright notice, this list of conditions and the following
+ *   disclaimer in the documentation and/or other materials provided
+ *   with the distribution.
+ *
+ * - Neither the name of the Eclipse Foundation, Inc. nor the
+ *   names of its contributors may be used to endorse or promote
+ *   products derived from this software without specific prior
+ *   written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
+ * CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
+ * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
+ * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+ * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+ * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
+ * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
+ * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+package org.eclipse.jgit.benchmarks;
+
+import java.io.IOException;
+import java.nio.file.FileStore;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.util.concurrent.TimeUnit;
+
+import org.eclipse.jgit.util.FileUtils;
+import org.openjdk.jmh.annotations.Benchmark;
+import org.openjdk.jmh.annotations.BenchmarkMode;
+import org.openjdk.jmh.annotations.Mode;
+import org.openjdk.jmh.annotations.OutputTimeUnit;
+import org.openjdk.jmh.annotations.Scope;
+import org.openjdk.jmh.annotations.Setup;
+import org.openjdk.jmh.annotations.State;
+import org.openjdk.jmh.annotations.TearDown;
+import org.openjdk.jmh.profile.StackProfiler;
+import org.openjdk.jmh.runner.Runner;
+import org.openjdk.jmh.runner.RunnerException;
+import org.openjdk.jmh.runner.options.Options;
+import org.openjdk.jmh.runner.options.OptionsBuilder;
+
+@State(Scope.Thread)
+public class LookupFileStoreBenchmark {
+
+	Path path;
+
+	@Setup
+	public void setupBenchmark() throws IOException {
+		path = Files.createTempFile("test", "x");
+	}
+
+	@TearDown
+	public void teardown() throws IOException {
+		FileUtils.delete(path.toFile(), FileUtils.RETRY);
+	}
+
+	@Benchmark
+	@BenchmarkMode({ Mode.AverageTime })
+	@OutputTimeUnit(TimeUnit.NANOSECONDS)
+	public FileStore testLookupFileStore() throws IOException {
+		FileStore fs = Files.getFileStore(path);
+		return fs;
+	}
+
+	public static void main(String[] args) throws RunnerException {
+		Options opt = new OptionsBuilder()
+				.include(LookupFileStoreBenchmark.class.getSimpleName())
+				.addProfiler(StackProfiler.class)
+				// .addProfiler(GCProfiler.class)
+				.forks(1).jvmArgs("-ea").build();
+		new Runner(opt).run();
+	}
+}