On 10/8/2018 12:41 PM, SZEDER Gábor wrote:

On Wed, Oct 03, 2018 at 03:18:05PM -0400, Jeff King wrote:

quoted

I'm still excited about the prospect of a bloom filter for paths which
each commit touches. I think that's the next big frontier in getting
things like "git log -- path" to a reasonable run-time.

There is certainly potential there.  With a (very) rough PoC
experiment, a 8MB bloom filter, and a carefully choosen path I can
achieve a nice, almost 25x speedup:

   $ time git rev-list --count HEAD -- t/valgrind/valgrind.sh
   6

   real    0m1.563s
   user    0m1.519s
   sys     0m0.045s

   $ time GIT_USE_POC_BLOOM_FILTER=y ~/src/git/git rev-list --count HEAD -- t/valgrind/valgrind.sh
   6

   real    0m0.063s
   user    0m0.043s
   sys     0m0.020s

   bloom filter total queries: 16269 definitely not: 16195 maybe: 74 false positives: 64 fp ratio: 0.003934

Nice! These numbers make sense to me, in terms of how many TREESAME 
queries we actually need to perform for such a query.

But I'm afraid it will take a while until I get around to turn it into
something presentable...

Do you have the code pushed somewhere public where one could take a 
look? I could provide some early feedback.

Thanks,
-Stolee