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| author | Ritesh Harjani <riteshh@linux.ibm.com> | 2020-09-18 08:06:35 +0300 |
|---|---|---|
| committer | Theodore Ts'o <tytso@mit.edu> | 2020-10-18 17:36:58 +0300 |
| commit | 9faac62d40131521973192e46a82d5066bb42c09 (patch) | |
| tree | aae393faf4ef585b38c70aedc85fd69a2b222ba9 /fs/ext4 | |
| parent | 7eb90a2d6a4817d73165a2a1addd5ead2fcb74b1 (diff) | |
| download | linux-9faac62d40131521973192e46a82d5066bb42c09.tar.xz | |
ext4: optimize file overwrites
In case if the file already has underlying blocks/extents allocated
then we don't need to start a journal txn and can directly return
the underlying mapping. Currently ext4_iomap_begin() is used by
both DAX & DIO path. We can check if the write request is an
overwrite & then directly return the mapping information.
This could give a significant perf boost for multi-threaded writes
specially random overwrites.
On PPC64 VM with simulated pmem(DAX) device, ~10x perf improvement
could be seen in random writes (overwrite). Also bcoz this optimizes
away the spinlock contention during jbd2 slab cache allocation
(jbd2_journal_handle). On x86 VM, ~2x perf improvement was observed.
Reported-by: Dan Williams <dan.j.williams@intel.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Ritesh Harjani <riteshh@linux.ibm.com>
Link: https://lore.kernel.org/r/88e795d8a4d5cd22165c7ebe857ba91d68d8813e.1600401668.git.riteshh@linux.ibm.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Diffstat (limited to 'fs/ext4')
| -rw-r--r-- | fs/ext4/inode.c | 18 |
1 files changed, 15 insertions, 3 deletions
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c index f1ee0229ac12..f81f45f5db73 100644 --- a/fs/ext4/inode.c +++ b/fs/ext4/inode.c @@ -3436,14 +3436,26 @@ static int ext4_iomap_begin(struct inode *inode, loff_t offset, loff_t length, map.m_len = min_t(loff_t, (offset + length - 1) >> blkbits, EXT4_MAX_LOGICAL_BLOCK) - map.m_lblk + 1; - if (flags & IOMAP_WRITE) + if (flags & IOMAP_WRITE) { + /* + * We check here if the blocks are already allocated, then we + * don't need to start a journal txn and we can directly return + * the mapping information. This could boost performance + * especially in multi-threaded overwrite requests. + */ + if (offset + length <= i_size_read(inode)) { + ret = ext4_map_blocks(NULL, inode, &map, 0); + if (ret > 0 && (map.m_flags & EXT4_MAP_MAPPED)) + goto out; + } ret = ext4_iomap_alloc(inode, &map, flags); - else + } else { ret = ext4_map_blocks(NULL, inode, &map, 0); + } if (ret < 0) return ret; - +out: ext4_set_iomap(inode, iomap, &map, offset, length); return 0; |