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Merge "Pack bitmaps: improve readability"

This commit is contained in:
Jonathan Nieder 2015-10-29 14:11:40 -04:00 committed by Gerrit Code Review @ Eclipse.org
parent e9a3dfe1dd c87b77bc31
commit f6b9cd38ca
1 changed files with 42 additions and 26 deletions
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68
org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/pack/PackWriterBitmapPreparer.java
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@ -181,8 +181,14 @@ Collection<BitmapCommit> selectCommits(int expectedCommitCount)
BitmapBuilder bitmap = entry.getBuilder();
int cardinality = bitmap.cardinality();
List<List<BitmapCommit>> running = new ArrayList<
List<BitmapCommit>>();
// Within this branch, keep ordered lists of commits representing
// chains in its history, where each chain is a "sub-branch".
// Ordering commits by these chains makes for fewer differences
// between consecutive selected commits, which in turn provides
// better compression/on the run-length encoding of the XORs between
// them.
List<List<BitmapCommit>> chains =
new ArrayList<List<BitmapCommit>>();
// Mark the current branch as inactive if its tip commit isn't
// recent and there are an excessive number of branches, to
@ -195,7 +201,8 @@ Collection<BitmapCommit> selectCommits(int expectedCommitCount)
}
// Insert bitmaps at the offsets suggested by the
// nextSelectionDistance() heuristic.
// nextSelectionDistance() heuristic. Only reuse bitmaps created
// for more distant commits.
int index = -1;
int nextIn = nextSpan(cardinality);
int nextFlg = nextIn == distantCommitSpan
@ -241,7 +248,8 @@ Collection<BitmapCommit> selectCommits(int expectedCommitCount)
}
}
// This commit is selected, calculate the next one.
// This commit is selected.
// Calculate where to look for the next one.
int flags = nextFlg;
nextIn = nextSpan(distanceFromTip);
nextFlg = nextIn == distantCommitSpan
@ -250,43 +258,48 @@ Collection<BitmapCommit> selectCommits(int expectedCommitCount)
BitmapBuilder fullBitmap = commitBitmapIndex.newBitmapBuilder();
rw.reset();
rw.markStart(c);
for (AnyObjectId objectId : selectionHelper.reusedCommits)
for (AnyObjectId objectId : selectionHelper.reusedCommits) {
rw.markUninteresting(rw.parseCommit(objectId));
}
rw.setRevFilter(
PackWriterBitmapWalker.newRevFilter(null, fullBitmap));
while (rw.next() != null) {
// Work is done in the RevFilter.
// The RevFilter adds the reachable commits from this
// selected commit to fullBitmap.
}
List<List<BitmapCommit>> matches = new ArrayList<
// Sort the commits by independent chains in its history,
// yielding better compression when building bitmaps.
List<List<BitmapCommit>> candidateChain = new ArrayList<
List<BitmapCommit>>();
for (List<BitmapCommit> list : running) {
BitmapCommit last = list.get(list.size() - 1);
if (fullBitmap.contains(last)) {
matches.add(list);
for (List<BitmapCommit> chain : chains) {
BitmapCommit mostRecentCommit = chain.get(chain.size() - 1);
if (fullBitmap.contains(mostRecentCommit)) {
candidateChain.add(chain);
}
}
List<BitmapCommit> match;
if (matches.isEmpty()) {
match = new ArrayList<BitmapCommit>();
running.add(match);
List<BitmapCommit> longestAncestorChain;
if (candidateChain.isEmpty()) {
longestAncestorChain = new ArrayList<BitmapCommit>();
chains.add(longestAncestorChain);
} else {
match = matches.get(0);
longestAncestorChain = candidateChain.get(0);
// Append to longest
for (List<BitmapCommit> list : matches) {
if (list.size() > match.size()) {
match = list;
for (List<BitmapCommit> chain : candidateChain) {
if (chain.size() > longestAncestorChain.size()) {
longestAncestorChain = chain;
}
}
}
match.add(new BitmapCommit(c, !match.isEmpty(), flags));
longestAncestorChain.add(new BitmapCommit(
c, !longestAncestorChain.isEmpty(), flags));
writeBitmaps.addBitmap(c, fullBitmap, 0);
}
for (List<BitmapCommit> list : running) {
selections.addAll(list);
for (List<BitmapCommit> chain : chains) {
selections.addAll(chain);
}
}
writeBitmaps.clearBitmaps(); // Remove the temporary commit bitmaps.
@ -329,6 +342,7 @@ private CommitSelectionHelper setupTipCommitBitmaps(RevWalk rw,
BitmapBuilder reuse = commitBitmapIndex.newBitmapBuilder();
List<BitmapCommit> reuseCommits = new ArrayList<BitmapCommit>();
for (PackBitmapIndexRemapper.Entry entry : bitmapRemapper) {
// More recent commits did not have the reuse flag set, so skip them
if ((entry.getFlags() & FLAG_REUSE) != FLAG_REUSE) {
continue;
}
@ -346,8 +360,8 @@ private CommitSelectionHelper setupTipCommitBitmaps(RevWalk rw,
}
}
// Do a RevWalk by commit time descending. Keep track of all the paths
// from the wants.
// Add branch tips that are not represented in old bitmap indices. Set
// up the RevWalk to walk the new commits not in the old packs.
List<BitmapBuilderEntry> tipCommitBitmaps = new ArrayList<BitmapBuilderEntry>(
want.size());
Set<RevCommit> peeledWant = new HashSet<RevCommit>(want.size());
@ -366,6 +380,8 @@ private CommitSelectionHelper setupTipCommitBitmaps(RevWalk rw,
}
// Create a list of commits in reverse order (older to newer).
// For each branch that contains the commit, mark its parents as being
// in the bitmap.
RevCommit[] commits = new RevCommit[expectedCommitCount];
int pos = commits.length;
RevCommit rc;
@ -480,7 +496,6 @@ int getFlags() {
*/
private static final class BitmapBuilderEntry {
private final RevCommit commit;
private final BitmapBuilder builder;
BitmapBuilderEntry(RevCommit commit, BitmapBuilder builder) {
@ -509,7 +524,6 @@ BitmapBuilder getBuilder() {
*/
private static final class CommitSelectionHelper implements Iterable<RevCommit> {
final Set<? extends ObjectId> peeledWants;
final List<BitmapBuilderEntry> tipCommitBitmaps;
final Iterable<BitmapCommit> reusedCommits;
final RevCommit[] commitsByOldest;
@ -527,6 +541,8 @@ private static final class CommitSelectionHelper implements Iterable<RevCommit>
}
public Iterator<RevCommit> iterator() {
// Member variables referenced by this iterator will have synthetic
// accessors generated for them if they are made private.
return new Iterator<RevCommit>() {
int pos = commitStartPos;