bcache, n.: a cache for arbitrary block devices that uses an SSD It's probably past time I started poking people to see about getting this stuff in. It's synced up with mainline, the documentation is for once relatively up to date, and it looks just about production ready.
Suggestions are more than welcome on how to make it easier to review - it's entirely too much code, I know (near 10k lines now). I'll be emailing the patches that touch other parts of the kernel separately. Short overview: Bcache does both writethrough and writeback caching. It presents itself as a new block device, a bit like say md. You can cache an arbitrary number of block devices with a single cache device, and attach and detach things at runtime - it's quite flexible. It's very fast. It uses a b+ tree for the index, along with a journal to coalesce index updates, and a bunch of other cool tricks like auxiliary binary search trees with software floating point keys to avoid a bunch of random memory accesses when doing binary searches in the btree. It does over 50k iops doing 4k random /writes/ without breaking a sweat, and would do many times that if I had faster hardware. It (configurably) tracks and skips sequential IO, so as to efficiently cache random IO. It's got more cool features than I can remember at this point. It's resilient, handling IO errors from the SSD when possible up to a configurable threshhold, then detaches the cache from the backing device even while you're still using it. The code is up at git://evilpiepirate.org/~kent/linux-bcache.git git://evilpiepirate.org/~kent/bcache-tools.git The wiki is woefully out of date, but that might change one day: http://bcache.evilpiepirate.org The most up to date documentation is in the kernel tree - Documentation/bcache.txt Documentation/ABI/testing/sysfs-block-bcache | 156 + Documentation/bcache.txt | 265 + block/Kconfig | 36 + block/Makefile | 4 + block/bcache.c | 8479 ++++++++++++++++++++++++++ block/bcache_util.c | 661 ++ block/bcache_util.h | 555 ++ fs/bio.c | 9 +- include/linux/blk_types.h | 2 + include/linux/sched.h | 4 + include/trace/events/bcache.h | 53 + kernel/fork.c | 3 + 12 files changed, 10225 insertions(+), 2 deletions(-) -- To unsubscribe from this list: send the line "unsubscribe linux-bcache" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
