Commits
Dave Chinner committed 756c6f0f7ef
xfs: reverse search directory freespace indexes When a directory is growing rapidly, new blocks tend to get added at the end of the directory. These end up at the end of the freespace index, and when the directory gets large finding these new freespaces gets expensive. The code does a linear search across the frespace index from the first block in the directory to the last, hence meaning the newly added space is the last index searched. Instead, do a reverse order index search, starting from the last block and index in the freespace index. This makes most lookups for free space on rapidly growing directories O(1) instead of O(N), but should not have any impact on random insert workloads because the average search length is the same regardless of which end of the array we start at. The result is a major improvement in large directory grow rates: create time(sec) / rate (files/s) File count vanilla Prev commit Patched 10k 0.41 / 24.3k 0.42 / 23.8k 0.41 / 24.3k 20k 0.74 / 27.0k 0.76 / 26.3k 0.75 / 26.7k 100k 3.81 / 26.4k 3.47 / 28.8k 3.27 / 30.6k 200k 8.58 / 23.3k 7.19 / 27.8k 6.71 / 29.8k 1M 85.69 / 11.7k 48.53 / 20.6k 37.67 / 26.5k 2M 280.31 / 7.1k 130.14 / 15.3k 79.55 / 25.2k 10M 3913.26 / 2.5k 552.89 / 18.1k Signed-off-by: Dave Chinner <dchinner@redhat.com> Reviewed-by: Christoph Hellwig <hch@lst.de> Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com> Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>