söndag 03 december 2006 05:59 skrev Shawn Pearce: > With the help of Robin Rosenberg I've been able to make jgit's log > operation run (on average) within a few milliseconds of core Git. > > Walking the 50,000 most recent commits from the Mozilla trunk[1]: > > $ time git rev-list --max-count=50000 HEAD >/dev/null > > core Git: 1.882s (average) > jgit: 1.932s (average) > > (times are with hot cache and from repeated executions) Nice indeed. That was a ten-fold improvement for getting my full history. So, just go on to the next case. I added filtering on filenames (yes, CVS-induced brain damage, I should track the content. next version. filenames are so much handier to work with). That gives me 4.5s to retrieve a filtered history (from 10800 commits).Half of the time is spent in re-sorting tree entries. Is that really necessary? > I think that is actually pretty good given that jgit is written > in Java using a fairly object-oriented design and has to deal with > some of the limitations of the language. Most of java's slowness comes from the programmers using it. (Lutz Prechelt. Technical opinion: comparing Java vs. C/C++ efficiency differences to interpersonal differences. ACM, Vol 42,#10, 1999) > One of the biggest annoyances has been the fact that although Java > 1.4 offers a way to mmap a file into the process, the overhead to > access that data seems to be far higher than just reading the file > content into a very large byte array, especially if we are going > to access that file content multiple times. So jgit performs worse > than core Git early on while it copies everything from the OS buffer > cache into the Java process, but then performs reasonably well once > the internal cache is hot. On the other hand using the mmap call > reduces early latency but hurts the access times so much that we're > talking closer to 3s average read times for the same log operation. Have you tried that with difference JVM's? -- robin - To unsubscribe from this list: send the line "unsubscribe git" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html