Hi Ted and Jan, I'm almost done with the first phase of this iomap conversion for regular file's buffered IO path, could you please take time to take a look at this series, I'd appreciated if I could get some feedback and comments before the next phase of development, or is there any plan to merge this series? Thanks, Yi. On 2024/4/10 22:29, Zhang Yi wrote: > Hello! > > This is the fourth version of RFC patch series that convert ext4 regular > file's buffered IO path to iomap and enable large folio. I've rebased it > on 6.9-rc3, it also **depends on my xfs/iomap fix series** which has > been reviewed but not merged yet[1]. Compared to the third vesion, this > iteration fixes an issue discovered in current ext4 code, and contains > another two main changes, 1) add bigalloc support and 2) simplify the > updating logic of reserved delalloc data block, both changes could be > sent out as preliminary patch series, besides these, others are some > small code cleanups, performance optimize and commit log improvements. > Please take a look at this series and any comments are welcome. > > This series supports ext4 with the default features and mount > options(bigalloc is also supported), doesn't support non-extent(ext3), > inline_data, dax, fs_verity, fs_crypt and data=journal mode, ext4 would > fall back to buffer_head path automatically if you enabled those > features or options. Although it has many limitations now, it can satisfy > the requirements of most common cases and bring a significant performance > benefit for large IOs. > > The iomap path would be simpler than the buffer_head path to some extent, > please note that there are 4 major differences: > 1. Always allocate unwritten extent for new blocks, it means that it's > not controlled by dioread_nolock mount option. > 2. Since 1, there is no risk of exposing stale data during the append > write, so we don't need to write back data before metadata, it's time > to drop 'data = ordered' mode automatically. > 3. Since 2, we don't need to reserve journal credits and use reserved > handle for the extent status conversion during writeback. > 4. We could postpone updating the i_disksize to the endio, it could > avoid exposing zero data during append write and instantaneous power > failure. > > Series details: > Patch 1-9: this is the part 2 preparation series, it fix a problem > first, and makes ext4_insert_delayed_block() call path support inserting > multiple delalloc blocks (also support bigalloc), finally make > ext4_da_map_blocks() buffer_head unaware, I've send it out separately[2] > and hope this could be merged first. > > Patch 10-19: this is the part 3 prepartory changes(picked out from my > metadata reservation series[3], these are not a strong dependency > patches, but I'd suggested these could be merged before the iomap > conversion). These patches moves ext4_da_update_reserve_space() to > ext4_es_insert_extent(), and always set EXT4_GET_BLOCKS_DELALLOC_RESERVE > when allocating delalloc blocks, no matter it's from delayed allocate or > non-delayed allocate (fallocate) path, it makes delalloc extents always > delonly. These can make delalloc reservation simpler and cleaner than > before. > > Patch 20-34: These patches are the main implements of the buffered IO > iomap conversion, It first introduce a sequence counter for extent > status tree, then add a new iomap aops for read, write, mmap, replace > current buffered_head path. Finally, enable iomap path besides inline > data, non-extent, dax, fs_verity, fs_crypt, defrag and data=journal > mode, if user specify "buffered_iomap" mount option, also enable large > folio. Please look at the following patch for details. > > About Tests: > - Pass kvm-xfstests in auto mode, and the keep running stress tests and > fault injection tests. > - A performance tests below (tested on my version 3 series, > theoretically there won't be much difference in this version). > > Fio tests with psync on my machine with Intel Xeon Gold 6240 CPU > with 400GB system ram, 200GB ramdisk and 1TB nvme ssd disk. > > == buffer read == > > buffer head iomap + large folio > type bs IOPS BW(MiB/s) IOPS BW(MiB/s) > ---------------------------------------------------- > hole 4K 565k 2206 811k 3167 > hole 64K 45.1k 2820 78.1k 4879 > hole 1M 2744 2744 4890 4891 > ramdisk 4K 436k 1703 554k 2163 > ramdisk 64K 29.6k 1848 44.0k 2747 > ramdisk 1M 1994 1995 2809 2809 > nvme 4K 306k 1196 324k 1267 > nvme 64K 19.3k 1208 24.3k 1517 > nvme 1M 1694 1694 2256 2256 > > == buffer write == > > buffer head iomap + large folio > type Overwrite Sync Writeback bs IOPS BW IOPS BW > ------------------------------------------------------------ > cache N N N 4K 395k 1544 415k 1621 > cache N N N 64K 30.8k 1928 80.1k 5005 > cache N N N 1M 1963 1963 5641 5642 > cache Y N N 4K 423k 1652 443k 1730 > cache Y N N 64K 33.0k 2063 80.8k 5051 > cache Y N N 1M 2103 2103 5588 5589 > ramdisk N N Y 4K 362k 1416 307k 1198 > ramdisk N N Y 64K 22.4k 1399 64.8k 4050 > ramdisk N N Y 1M 1670 1670 4559 4560 > ramdisk N Y N 4K 9830 38.4 13.5k 52.8 > ramdisk N Y N 64K 5834 365 10.1k 629 > ramdisk N Y N 1M 1011 1011 2064 2064 > ramdisk Y N Y 4K 397k 1550 409k 1598 > ramdisk Y N Y 64K 29.2k 1827 73.6k 4597 > ramdisk Y N Y 1M 1837 1837 4985 4985 > ramdisk Y Y N 4K 173k 675 182k 710 > ramdisk Y Y N 64K 17.7k 1109 33.7k 2105 > ramdisk Y Y N 1M 1128 1129 1790 1791 > nvme N N Y 4K 298k 1164 290k 1134 > nvme N N Y 64K 21.5k 1343 57.4k 3590 > nvme N N Y 1M 1308 1308 3664 3664 > nvme N Y N 4K 10.7k 41.8 12.0k 46.9 > nvme N Y N 64K 5962 373 8598 537 > nvme N Y N 1M 676 677 1417 1418 > nvme Y N Y 4K 366k 1430 373k 1456 > nvme Y N Y 64K 26.7k 1670 56.8k 3547 > nvme Y N Y 1M 1745 1746 3586 3586 > nvme Y Y N 4K 59.0k 230 61.2k 239 > nvme Y Y N 64K 13.0k 813 21.0k 1311 > nvme Y Y N 1M 683 683 1368 1369 > > TODO > - Keep on doing stress tests and fixing. > - Reserve enough space for delalloc metadata blocks and try to drop > ext4_nonda_switch(). > - First support defrag and then support other more unsupported features > and mount options. > > Changes since v3: > - Drop the part 1 prepartory patches which have been merged [4]. > - Drop the two iomap patches since I've submitted separately [1]. > - Fix an incorrect reserved delalloc blocks count and incorrect extent > status cache issue found on current ext4 code. > - Pick out part 2 prepartory patch series [2], it make > ext4_insert_delayed_block() call path support inserting multiple > delalloc blocks (also support bigalloc )and make ext4_da_map_blocks() > buffer_head unaware. > - Adjust and simplify the reserved delalloc blocks updating logic, > preparing for reserving meta data blocks for delalloc. > - Drop datasync dirty check in ext4_set_iomap() for buffered > read/write, improves the concurrent performance on small I/Os. > - Prevent always hold invalid_lock in page_cache_ra_order(), add > lockless check. > - Disable iomap path by default since it's experimental new, add a > mount option "buffered_iomap" to enable it. > - Some other minor fixes and change log improvements. > Changes since v2: > - Update patch 1-6 to v3. > - iomap_zero and iomap_unshare don't need to update i_size and call > iomap_write_failed(), introduce a new helper iomap_write_end_simple() > to avoid doing that. > - Factor out ext4_[ext|ind]_map_blocks() parts from ext4_map_blocks(), > introduce a new helper ext4_iomap_map_one_extent() to allocate > delalloc blocks in writeback, which is always under i_data_sem in > write mode. This is done to prevent the writing back delalloc > extents become stale if it raced by truncate. > - Add a lock detection in mapping_clear_large_folios(). > Changes since v1: > - Introduce seq count for iomap buffered write and writeback to protect > races from extents changes, e.g. truncate, mwrite. > - Always allocate unwritten extents for new blocks, drop dioread_lock > mode, and make no distinctions between dioread_lock and > dioread_nolock. > - Don't add ditry data range to jinode, drop data=ordered mode, and > make no distinctions between data=ordered and data=writeback mode. > - Postpone updating i_disksize to endio. > - Allow splitting extents and use reserved space in endio. > - Instead of reimplement a new delayed mapping helper > ext4_iomap_da_map_blocks() for buffer write, try to reuse > ext4_da_map_blocks(). > - Add support for disabling large folio on active inodes. > - Support online defragmentation, make file fall back to buffer_head > and disable large folio in ext4_move_extents(). > - Move ext4_nonda_switch() in advance to prevent deadlock in mwrite. > - Add dirty_len and pos trace info to trace_iomap_writepage_map(). > - Update patch 1-6 to v2. > > [1] https://lore.kernel.org/linux-xfs/20240320110548.2200662-1-yi.zhang@xxxxxxxxxxxxxxx/ > [2] https://lore.kernel.org/linux-ext4/20240410034203.2188357-1-yi.zhang@xxxxxxxxxxxxxxx/ > [3] https://lore.kernel.org/linux-ext4/20230824092619.1327976-1-yi.zhang@xxxxxxxxxxxxxxx/ > [4] https://lore.kernel.org/linux-ext4/20240105033018.1665752-1-yi.zhang@xxxxxxxxxxxxxxx/ > > Thanks, > Yi. > > --- > v3: https://lore.kernel.org/linux-ext4/20240127015825.1608160-1-yi.zhang@xxxxxxxxxxxxxxx/ > v2: https://lore.kernel.org/linux-ext4/20240102123918.799062-1-yi.zhang@xxxxxxxxxxxxxxx/ > v1: https://lore.kernel.org/linux-ext4/20231123125121.4064694-1-yi.zhang@xxxxxxxxxxxxxxx/ > > Zhang Yi (34): > ext4: factor out a common helper to query extent map > ext4: check the extent status again before inserting delalloc block > ext4: trim delalloc extent > ext4: drop iblock parameter > ext4: make ext4_es_insert_delayed_block() insert multi-blocks > ext4: make ext4_da_reserve_space() reserve multi-clusters > ext4: factor out check for whether a cluster is allocated > ext4: make ext4_insert_delayed_block() insert multi-blocks > ext4: make ext4_da_map_blocks() buffer_head unaware > ext4: factor out ext4_map_create_blocks() to allocate new blocks > ext4: optimize the EXT4_GET_BLOCKS_DELALLOC_RESERVE flag set > ext4: don't set EXTENT_STATUS_DELAYED on allocated blocks > ext4: let __revise_pending() return newly inserted pendings > ext4: count removed reserved blocks for delalloc only extent entry > ext4: update delalloc data reserve spcae in ext4_es_insert_extent() > ext4: drop ext4_es_delayed_clu() > ext4: use ext4_map_query_blocks() in ext4_map_blocks() > ext4: drop ext4_es_is_delonly() > ext4: drop all delonly descriptions > ext4: use reserved metadata blocks when splitting extent on endio > ext4: introduce seq counter for the extent status entry > ext4: add a new iomap aops for regular file's buffered IO path > ext4: implement buffered read iomap path > ext4: implement buffered write iomap path > ext4: implement writeback iomap path > ext4: implement mmap iomap path > ext4: implement zero_range iomap path > ext4: writeback partial blocks before zeroing out range > ext4: fall back to buffer_head path for defrag > ext4: partial enable iomap for regular file's buffered IO path > filemap: support disable large folios on active inode > ext4: enable large folio for regular file with iomap buffered IO path > ext4: don't mark IOMAP_F_DIRTY for buffer write > ext4: add mount option for buffered IO iomap path >
