The Summer of Code officially started a couple of weeks ago, so I've been getting started on my project. I've not written any actual code yet, but have been busy with other aspects of the project. First of all I have been reading a bit of documentation and code relevant to dirhash itself and FreeBSD memory management. I have a lot to learn, especially about the memory stuff. The two approaches I am looking at, mentioned in the USENIX paper by Ian Dowse and David Malone (my SoC mentor), are to either use the buffer cache for dirhash's memory so the VM can take care of providing memory as it is available, or to use a method for allocating memory where the kernel can signal for some to be freed in low memory situations, perhaps using the slab allocator.
I have also been learning a little bit about Perforce, the version control system used by FreeBSD for experimental projects. I have not used Perforce before this, and it is a bit different from the VCSs I've used before (CVS and Subversion). Also, I have done a bit of experimentation with the current dirhash implementation just to be sure that it can free memory it no longer needs. This was just a simple test where I created a directory with a couple of million entries, checked the vfs.ufs.dirhash_mem sysctl, removed the directory, then checked vfs.ufs.dirhash_mem again to make sure the memory used had decreased. It had. Finally, I sent off a brief proposal to do a talk about this project at EuroBSDCon 2008. Obviously I don't have much to create a talk with yet, but I should by the end of the summer. Plus, the second day of EuroBSDCon this year happens to fall on my birthday, and I think hanging out with fellow BSD nerds in France could be a fun birthday activity :)
