5d446f410d
Some packs built by JGit have incredibly long delta chains due to a long standing bug in PackWriter. Google has packs created by JGit's DfsGarbageCollector with chains of 6000 objects long, or more. Inflating objects at the end of this 6000 long chain is impossible to complete within a reasonable time bound. It could take a beefy system hours to perform even using the heavily optimized native C implementation of Git, let alone with JGit. Enable pack.cutDeltaChains to be set in a configuration file to permit the PackWriter to determine the length of each delta chain and clip the chain at arbitrary points to fit within pack.depth. Delta chain cycles are still possible, but no attempt is made to detect them. A trivial chain of A->B->A will iterate for the full pack.depth configured limit (e.g. 50) and then pick an object to store as non-delta. When cutting chains the object list is walked in reverse to try and take advantage of existing chain computations. The assumption here is most deltas are near the end of the list, and their bases are near the front of the list. Going up from the tail attempts to reuse chainLength computations by relying on the memoized value in the delta base. The chainLength field in ObjectToPack is overloaded into the depth field normally used by DeltaWindow. This is acceptable because the chain cut happens before delta search, and the chainLength is reset to 0 if delta search will follow. Change-Id: Ida4fde9558f3abbbb77ade398d2af3941de9c812 |
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| .settings | ||
| META-INF | ||
| findBugs | ||
| resources/org/eclipse/jgit/internal | ||
| src/org/eclipse/jgit | ||
| .classpath | ||
| .fbprefs | ||
| .gitignore | ||
| .project | ||
| about.html | ||
| build.properties | ||
| plugin.properties | ||
| pom.xml | ||