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BasePackFetchConnection: Skip object/ref lookups if local repo is empty 

When cloning repository some of the operations in
`BasePackFetchConnection` can be skipped. We don't need to advertise
packs, compute "wanted time" or wanted refs to send. All of those
operations will try to read objects from an empty repository which
always results in a missing object.

This saves 99.9% of `LooseObjects.open()` calls which dramatically
speeds up object negotiation in V2 protocol.

In testing on JGit (v6.8.0.202311291450-r) repository, which contains
564 refs, the number of calls to `LooseObjects.open()` was reduced from
1187 to 1.

Skipping a call to `markRefsAdvertised()` initially reduced be above
number to 623. Then assuming "0" "want time" an on empty repository
pushed the calls down to 312. Finally, skipping objects reachability on
empty repository set calls down to 1.

The last call is performed from `FetchProcess.asForIsComplete()` which
probably needs to stay in place.

Bug: jgit-5
Change-Id: I2480690726ea54d3b1593380bc8f8d15b4d6afc6
This commit is contained in:
Dariusz Luksza 2023-12-18 18:24:49 +00:00
parent faa50c683d
commit 7884873160
1 changed files with 20 additions and 9 deletions
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29
org.eclipse.jgit/src/org/eclipse/jgit/transport/BasePackFetchConnection.java
View File

@ -402,11 +402,14 @@ private void clearState() {
protected void doFetch(final ProgressMonitor monitor,
final Collection<Ref> want, final Set<ObjectId> have,
OutputStream outputStream) throws TransportException {
boolean hasObjects = !have.isEmpty();
try {
noProgress = monitor == NullProgressMonitor.INSTANCE;
markRefsAdvertised();
markReachable(want, have, maxTimeWanted(want));
if (hasObjects) {
markRefsAdvertised();
}
markReachable(want, have, maxTimeWanted(want, hasObjects));
if (TransferConfig.ProtocolVersion.V2
.equals(getProtocolVersion())) {
@ -418,7 +421,7 @@ protected void doFetch(final ProgressMonitor monitor,
state = new TemporaryBuffer.Heap(Integer.MAX_VALUE);
pckState = new PacketLineOut(state);
try {
doFetchV2(monitor, want, outputStream);
doFetchV2(monitor, want, outputStream, hasObjects);
} finally {
clearState();
}
@ -430,7 +433,7 @@ protected void doFetch(final ProgressMonitor monitor,
pckState = new PacketLineOut(state);
}
PacketLineOut output = statelessRPC ? pckState : pckOut;
if (sendWants(want, output)) {
if (sendWants(want, output, hasObjects)) {
boolean mayHaveShallow = depth != null || deepenSince != null || !deepenNots.isEmpty();
Set<ObjectId> shallowCommits = local.getObjectDatabase().getShallowCommits();
if (isCapableOf(GitProtocolConstants.CAPABILITY_SHALLOW)) {
@ -457,7 +460,8 @@ protected void doFetch(final ProgressMonitor monitor,
}
private void doFetchV2(ProgressMonitor monitor, Collection<Ref> want,
OutputStream outputStream) throws IOException, CancelledException {
OutputStream outputStream, boolean hasObjects)
throws IOException, CancelledException {
sideband = true;
negotiateBegin();
@ -479,7 +483,7 @@ private void doFetchV2(ProgressMonitor monitor, Collection<Ref> want,
pckState.writeString(capability);
}
if (!sendWants(want, pckState)) {
if (!sendWants(want, pckState, hasObjects)) {
// We already have everything we wanted.
return;
}
@ -666,8 +670,12 @@ FetchConfig getFetchConfig() {
return local.getConfig().get(FetchConfig::new);
}
private int maxTimeWanted(Collection<Ref> wants) {
private int maxTimeWanted(Collection<Ref> wants, boolean hasObjects) {
int maxTime = 0;
if (!hasObjects) {
// we don't have any objects locally, we can immediately bail out
return maxTime;
}
for (Ref r : wants) {
try {
final RevObject obj = walk.parseAny(r.getObjectId());
@ -769,7 +777,8 @@ private void markReachable(ObjectId id) {
}
}
private boolean sendWants(Collection<Ref> want, PacketLineOut p)
private boolean sendWants(Collection<Ref> want, PacketLineOut p,
boolean hasObjects)
throws IOException {
boolean first = true;
for (Ref r : want) {
@ -778,7 +787,9 @@ private boolean sendWants(Collection<Ref> want, PacketLineOut p)
continue;
}
// if depth is set we need to fetch the objects even if they are already available
if (transport.getDepth() == null) {
if (transport.getDepth() == null
// only check reachable objects when we have objects
&& hasObjects) {
try {
if (walk.parseAny(objectId).has(REACHABLE)) {
// We already have this object. Asking for it is