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Add GC_REST PackSource to better order DFS packs 

Force reads to use a search ordering of:

  INSERT / RECEIVE
  COMPACT
  GC (heads)
  GC_REST (non-heads)
  GC_TXN (refs/txn)
  UNREACHABLE_GARBAGE

This has provided decent performance for object lookups.  Starting
from an arbitrary reference may find the content in a newer pack
created by DfsObjectInserter or a ReceivePack server.  Compaction of
recent packs also contains newer content, and then most interesting
data is in the "main" GC pack.  As the GC pack is self-contained (has
no edges leading outside) readers typically do not need to go further.

Adding a new GC_REST PackSource allows the DfsGarbageCollector to
identify to the pack ordering code which pack is which, so the
non-heads are scanned second during reads.  This removes a hack that
was unique to Google's implementation that enforced this behavior by
fixing up the lastModified timestamp.

Renumber the PackSource's categories to reflect this search ordering.

Change-Id: I19fdaab8a8d6687cbe8c88488e6daa0630bf189a
This commit is contained in:
Shawn Pearce 2016-06-26 10:58:38 -07:00
parent 5fe44ed3ee
commit 30eb6423a2
2 changed files with 25 additions and 20 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/dfs/DfsGarbageCollector.java
View File

@ -44,6 +44,7 @@
package org.eclipse.jgit.internal.storage.dfs;
import static org.eclipse.jgit.internal.storage.dfs.DfsObjDatabase.PackSource.GC;
import static org.eclipse.jgit.internal.storage.dfs.DfsObjDatabase.PackSource.GC_REST;
import static org.eclipse.jgit.internal.storage.dfs.DfsObjDatabase.PackSource.GC_TXN;
import static org.eclipse.jgit.internal.storage.dfs.DfsObjDatabase.PackSource.UNREACHABLE_GARBAGE;
import static org.eclipse.jgit.internal.storage.pack.PackExt.BITMAP_INDEX;
@ -299,6 +300,7 @@ private void packHeads(ProgressMonitor pm) throws IOException {
writePack(GC, pw, pm);
}
}
private void packRest(ProgressMonitor pm) throws IOException {
if (nonHeads.isEmpty())
return;
@ -308,7 +310,7 @@ private void packRest(ProgressMonitor pm) throws IOException {
pw.excludeObjects(packedObjs);
pw.preparePack(pm, nonHeads, allHeads);
if (0 < pw.getObjectCount())
writePack(GC, pw, pm);
writePack(GC_REST, pw, pm);
}
}

41
org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/dfs/DfsObjDatabase.java
View File

@ -79,24 +79,6 @@ public static enum PackSource {
*/
RECEIVE(0),
/**
* Pack was created by Git garbage collection by this implementation.
* <p>
* This source is only used by the {@link DfsGarbageCollector} when it
* builds a pack file by traversing the object graph and copying all
* reachable objects into a new pack stream.
*
* @see DfsGarbageCollector
*/
GC(1),
/**
* RefTreeGraph pack was created by Git garbage collection.
*
* @see DfsGarbageCollector
*/
GC_TXN(1),
/**
* The pack was created by compacting multiple packs together.
* <p>
@ -108,6 +90,27 @@ public static enum PackSource {
*/
COMPACT(1),
/**
* Pack was created by Git garbage collection by this implementation.
* <p>
* This source is only used by the {@link DfsGarbageCollector} when it
* builds a pack file by traversing the object graph and copying all
* reachable objects into a new pack stream.
*
* @see DfsGarbageCollector
*/
GC(2),
/** Created from non-heads by {@link DfsGarbageCollector}. */
GC_REST(3),
/**
* RefTreeGraph pack was created by Git garbage collection.
*
* @see DfsGarbageCollector
*/
GC_TXN(4),
/**
* Pack was created by Git garbage collection.
* <p>
@ -115,7 +118,7 @@ public static enum PackSource {
* last GC pass. It is retained in a new pack until it is safe to prune
* these objects from the repository.
*/
UNREACHABLE_GARBAGE(2);
UNREACHABLE_GARBAGE(5);
final int category;