From: Gao Xiang <hsiangkao@xxxxxxxxxx> Hi folks, This version addresses previous comments mentioned in https://lore.kernel.org/r/20210330142531.19809-1-hsiangkao@xxxxxxx Changelog since v3: - drop the modifications to the bad inode list suggested by Dave on IRC (since the patchset forms well, even AVL tree optimization is another story); - update a comment suggested by Darrick. Original description: Phase 6 is single threaded, processing a single AG at a time and a single directory inode at a time. Phase 6 if often IO latency bound despite the prefetching it does, resulting in low disk utilisation and high runtimes. The solution for this is the same as phase 3 and 4 - scan multiple AGs at once for directory inodes to process. This patch set enables phase 6 to scan multiple AGS at once, and hence requires concurrent updates of inode records as tehy can be accessed and modified by multiple scanning threads now. We also need to protect the bad inodes list from concurrent access and then we can enable concurrent processing of directories. However, directory entry checking and reconstruction can also be CPU bound - large directories overwhelm the directory name hash structures because the algorithms have poor scalability - one is O(n + n^2), another is O(n^2) when the number of dirents greatly outsizes the hash table sizes. Hence we need to more than just parallelise across AGs - we need to parallelise processing within AGs so that a single large directory doesn't completely serialise processing within an AG. This is done by using bound-depth workqueues to allow inode records to be processed asynchronously as the inode records are fetched from disk. Further, we need to fix the bad alogrithmic scalability of the in memory directory tracking structures. This is done through a combination of better structures and more appropriate dynamic size choices. The results on a filesystem with a single 10 million entry directory containing 400MB of directory entry data is as follows: v5.6.0 (Baseline) XFS_REPAIR Summary Thu Oct 22 12:10:52 2020 Phase Start End Duration Phase 1: 10/22 12:06:41 10/22 12:06:41 Phase 2: 10/22 12:06:41 10/22 12:06:41 Phase 3: 10/22 12:06:41 10/22 12:07:00 19 seconds Phase 4: 10/22 12:07:00 10/22 12:07:12 12 seconds Phase 5: 10/22 12:07:12 10/22 12:07:13 1 second Phase 6: 10/22 12:07:13 10/22 12:10:51 3 minutes, 38 seconds Phase 7: 10/22 12:10:51 10/22 12:10:51 Total run time: 4 minutes, 10 seconds real 4m11.151s user 4m20.083s sys 0m14.744s 5.9.0-rc1 + patchset: XFS_REPAIR Summary Thu Oct 22 13:19:02 2020 Phase Start End Duration Phase 1: 10/22 13:18:09 10/22 13:18:09 Phase 2: 10/22 13:18:09 10/22 13:18:09 Phase 3: 10/22 13:18:09 10/22 13:18:31 22 seconds Phase 4: 10/22 13:18:31 10/22 13:18:45 14 seconds Phase 5: 10/22 13:18:45 10/22 13:18:45 Phase 6: 10/22 13:18:45 10/22 13:19:00 15 seconds Phase 7: 10/22 13:19:00 10/22 13:19:00 Total run time: 51 seconds real 0m52.375s user 1m3.739s sys 0m20.346s Performance improvements on filesystems with small directories and really fast storage are, at best, modest. The big improvements are seen with either really large directories and/or relatively slow devices that are IO latency bound and can benefit from having more IO in flight at once. Thanks, Gao Xiang Dave Chinner (7): workqueue: bound maximum queue depth repair: Protect bad inode list with mutex repair: protect inode chunk tree records with a mutex repair: parallelise phase 6 repair: don't duplicate names in phase 6 repair: convert the dir byaddr hash to a radix tree repair: scale duplicate name checking in phase 6. libfrog/radix-tree.c | 46 +++++ libfrog/workqueue.c | 42 ++++- libfrog/workqueue.h | 4 + repair/dir2.c | 34 ++-- repair/dir2.h | 2 +- repair/incore.h | 23 +++ repair/incore_ino.c | 15 ++ repair/phase6.c | 395 +++++++++++++++++++++---------------------- 8 files changed, 339 insertions(+), 222 deletions(-) -- 2.20.1
