On 2012-02-01, at 12:26 AM, Tao Ma wrote: > On 02/01/2012 06:33 AM, Allison Henderson wrote: >> Hi Yongqiang, >> >> I've have been working on an extent lock implementation that uses an >> rbtree to keep track of locked extents, and I think I will probably end >> up with a something similar to the tree that you've already set up for >> delayed extents. So I wanted to send a note out to see what folks would >> think about the idea of merging the two solutions. >> >> If we did this, the tree would get a little more complex in that it >> would have to keep track of more than just delayed extents. It would >> have to keep track of all extents and the processes that are waiting on >> them. So I guess it would kind of turn into an extent status tree. I >> also realize that some folks wanted to see range locks go into /lib as >> general purpose code so that other filesystems or kernel code could use >> it too, but the advantage to this approach would be one less tree for >> ext4 to keep track of. Any thoughts? > > We (Taobao) are very interested in this stuff and it should benefit > several of our workload(It is on our todo list for a long time). I guess > Yongqiang's solution is a little bit limited to the only delayed extent > case, and your new solution at least has 2 more benefits: > 1. improve the direct i/o read/write > 2. speed up the extent search since now we only cache one in > ei_cached_extent. Another related usage is to use a tree to track free extents in the block allocation bitmaps. We already have a thread starting at mount time to do itable_init, and it would be possible to have that same thread read block bitmaps from disk and generate a free extents tree. That would allow much faster extent allocation without changing the on-disk format. Cheers, Andreas -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
