DAX PMDs have been disabled since Jan Kara introduced DAX radix tree based locking. This series allows DAX PMDs to participate in the DAX radix tree based locking scheme so that they can be re-enabled. Jan and Christoph, can you please help review these changes? Andrew, when the time is right can you please push these changes to Linus via the -mm tree? In some simple mmap I/O testing with FIO the use of PMD faults more than doubles I/O performance as compared with PTE faults. Here is the FIO script I used for my testing: [global] bs=4k size=2G directory=/mnt/pmem0 ioengine=mmap [randrw] rw=randrw Here are the performance results with XFS using only pte faults: READ: io=1022.7MB, aggrb=557610KB/s, minb=557610KB/s, maxb=557610KB/s, mint=1878msec, maxt=1878msec WRITE: io=1025.4MB, aggrb=559084KB/s, minb=559084KB/s, maxb=559084KB/s, mint=1878msec, maxt=1878msec Here are performance numbers for that same test using PMD faults: READ: io=1022.7MB, aggrb=1406.7MB/s, minb=1406.7MB/s, maxb=1406.7MB/s, mint=727msec, maxt=727msec WRITE: io=1025.4MB, aggrb=1410.4MB/s, minb=1410.4MB/s, maxb=1410.4MB/s, mint=727msec, maxt=727msec This was done on a random lab machine with a PMEM device made from memmap'd RAM. To get XFS to use PMD faults, I did the following: mkfs.xfs -f -d su=2m,sw=1 /dev/pmem0 mount -o dax /dev/pmem0 /mnt/pmem0 xfs_io -c "extsize 2m" /mnt/pmem0 Changes since v2: - Removed the struct buffer_head + get_block_t based dax_pmd_fault() handler. All DAX PMD faults will now happen via the new struct iomap based iomap_dax_pmd_fault(). - Added a new struct iomap based PMD path which is now used by XFS. - Now that it is using struct iomap, ext2 no longer needs to modified so that ext2_get_block() will give us the size of a hole. - Remove support for DAX PMD faults for ext2. I can't get them to reliably happen in my testing. - Removed unused xfs_get_blocks_dax_fault() wrapper - Added a bunch of comments around my changes in dax.c. This was built upon xfs/for-next with PMD performance fixes from Toshi Kani and Dan Williams. Dan's patch has already been merged for v4.8, and Toshi's patches are currently queued in Andrew Morton's mm tree for v4.9 inclusion. Here is a tree containing my changes and all the fixes that I've been testing: https://git.kernel.org/cgit/linux/kernel/git/zwisler/linux.git/log/?h=dax_pmd_v3 Ross Zwisler (11): ext4: allow DAX writeback for hole punch ext4: tell DAX the size of allocation holes dax: remove buffer_size_valid() ext2: remove support for DAX PMD faults dax: make 'wait_table' global variable static dax: consistent variable naming for DAX entries dax: coordinate locking for offsets in PMD range dax: remove dax_pmd_fault() dax: add struct iomap based DAX PMD support xfs: use struct iomap based DAX PMD fault path dax: remove "depends on BROKEN" from FS_DAX_PMD fs/Kconfig | 1 - fs/dax.c | 696 +++++++++++++++++++++++++++++----------------------- fs/ext2/file.c | 24 +- fs/ext4/inode.c | 7 +- fs/xfs/xfs_aops.c | 25 +- fs/xfs/xfs_aops.h | 3 - fs/xfs/xfs_file.c | 2 +- include/linux/dax.h | 37 ++- mm/filemap.c | 6 +- 9 files changed, 434 insertions(+), 367 deletions(-) -- 2.7.4 -- 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
