On Thu, Jun 27, 2013 at 09:07:38AM -0700, Shawn O. Pearce wrote: > > And the pack-order versus idx-order for the bitmaps is still up in the > > air. Do we have numbers on the on-disk sizes of the resulting EWAHs? > > I did not see any presented in this thread, and I am very interested > in this aspect of the series. The path hash cache should be taking > about 9.9M of disk space, but I recall reading the bitmap file is 8M. > I don't understand.
I don't know there the 8M number came from, or if it was on the kernel repo. My bitmap-enabled pack of linux-2.6 (about 3.2M objects) using Vicent's patches looks like: $ du -sh * 42M pack-9ea76831aec6c49c5ff42509a2a2ce97da13c5ad.bitmap 87M pack-9ea76831aec6c49c5ff42509a2a2ce97da13c5ad.idx 630M pack-9ea76831aec6c49c5ff42509a2a2ce97da13c5ad.pack Packing the same repo with "jgit debug-gc" (jgit 3.0.0) yields: $ du -sh * 3.0M pack-2478783825733a1f1012f0087a0b5a92aa7437d8.bitmap 82M pack-2478783825733a1f1012f0087a0b5a92aa7437d8.idx 585M pack-2478783825733a1f1012f0087a0b5a92aa7437d8.pack 4.8M pack-f61fb76112372288923be7a0464476892dfebe3e.idx 97M pack-f61fb76112372288923be7a0464476892dfebe3e.pack If we assume that 12M of that is name-hash, that's still an order of magnitude larger. For reference, jgit created 327 bitmaps (according to its progress eye candy), and Vicent's patches generated 385. So that explains some of the increase, but the per-bitmap size is still much larger. > The path hash cache may still be required, Colby and I have been > debating the merits of having the data available for delta compression > vs. the increase in memory required to hold it. I guess this is not an option for JGit, but for C git, an mmap-able name-hash file means we can just fault in the pages mentioning objects we actually need it for. And its use can be completely optional; in fact, it doesn't even need to be inside the .bitmap file (though I cannot think of a reason it would be useful outside of having bitmaps). -Peff -- To unsubscribe from this list: send the line "unsubscribe git" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html