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Simplify size test in PackWriter 

Clip the configured limit to Integer.MAX_VALUE at the top of the
loop, saving a compare branch per object considered. This can cut
2M branches out of a repacking of the Linux kernel.

Rewrite the logic so the primary path is to match the conditional;
most objects are larger than BLKSZ (16 bytes) and less than limit.
This may help branch prediction on CPUs if the CPU tries to assume
execution takes the side of the branch and not the second.

Change-Id: I5133d1651640939afe9fbcfd8cfdb59965c57d5a
This commit is contained in:
Shawn Pearce 2013-04-04 11:23:16 -07:00
parent d45277a691
commit 93a27ce728
1 changed files with 6 additions and 8 deletions
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14
org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/pack/PackWriter.java
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@ -1147,7 +1147,9 @@ private void searchForDeltas(ProgressMonitor monitor)
AsyncObjectSizeQueue<ObjectToPack> sizeQueue = reader.getObjectSize(
Arrays.<ObjectToPack> asList(list).subList(0, cnt), false);
try {
final long limit = config.getBigFileThreshold();
final long limit = Math.min(
config.getBigFileThreshold(),
Integer.MAX_VALUE);
for (;;) {
try {
if (!sizeQueue.next())
@ -1175,14 +1177,10 @@ private void searchForDeltas(ProgressMonitor monitor)
otp = objectsMap.get(sizeQueue.getObjectId());
long sz = sizeQueue.getSize();
if (limit <= sz || Integer.MAX_VALUE <= sz)
otp.setDoNotDelta(); // too big, avoid costly files
else if (sz <= DeltaIndex.BLKSZ)
otp.setDoNotDelta(); // too small, won't work
else
if (DeltaIndex.BLKSZ < sz && sz < limit)
otp.setWeight((int) sz);
else
otp.setDoNotDelta(); // too small, or too big
monitor.update(1);
}
} finally {