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Reduce contention on PackFile.idx() function. 

In case of concurrent pack file access, threads may wait on the idx()
function even for already open files. This happens especially with a
slow file system.

Performance numbers are listed in the bug report.

Bug: 543739
Change-Id: Iff328d347fa65ae07ecce3267d44184161248978
Signed-off-by: Juergen Denner <j.denner@sap.com>
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>
This commit is contained in:
Juergen Denner 2019-01-15 13:22:54 +01:00 committed by Matthias Sohn
parent 7b3ee6f62e
commit 19c4380689
1 changed files with 34 additions and 25 deletions
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59
org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/file/PackFile.java
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@ -139,7 +139,7 @@ public int compare(final PackFile a, final PackFile b) {
private byte[] packChecksum;
private PackIndex loadedIdx;
private volatile PackIndex loadedIdx;
private PackReverseIndex reverseIdx;
@ -174,35 +174,44 @@ public PackFile(final File packFile, int extensions) {
length = Long.MAX_VALUE;
}
private synchronized PackIndex idx() throws IOException {
if (loadedIdx == null) {
if (invalid)
throw new PackInvalidException(packFile);
private PackIndex idx() throws IOException {
PackIndex idx = loadedIdx;
if (idx == null) {
synchronized (this) {
idx = loadedIdx;
if (idx == null) {
if (invalid) {
throw new PackInvalidException(packFile);
}
try {
idx = PackIndex.open(extFile(INDEX));
try {
final PackIndex idx = PackIndex.open(extFile(INDEX));
if (packChecksum == null) {
packChecksum = idx.packChecksum;
} else if (!Arrays.equals(packChecksum, idx.packChecksum)) {
throw new PackMismatchException(MessageFormat.format(
JGitText.get().packChecksumMismatch,
packFile.getPath(),
ObjectId.fromRaw(packChecksum).name(),
ObjectId.fromRaw(idx.packChecksum).name()));
if (packChecksum == null) {
packChecksum = idx.packChecksum;
} else if (!Arrays.equals(packChecksum,
idx.packChecksum)) {
throw new PackMismatchException(MessageFormat
.format(JGitText.get().packChecksumMismatch,
packFile.getPath(),
ObjectId.fromRaw(packChecksum)
.name(),
ObjectId.fromRaw(idx.packChecksum)
.name()));
}
loadedIdx = idx;
} catch (InterruptedIOException e) {
// don't invalidate the pack, we are interrupted from
// another thread
throw e;
} catch (IOException e) {
invalid = true;
throw e;
}
}
loadedIdx = idx;
} catch (InterruptedIOException e) {
// don't invalidate the pack, we are interrupted from another thread
throw e;
} catch (IOException e) {
invalid = true;
throw e;
}
}
return loadedIdx;
return idx;
}
/** @return the File object which locates this pack on disk. */
public File getPackFile() {
return packFile;