Re: [PATCH] md/raid5: set chunk_sectors to enable full stripe I/O splitting

[Yu Kuai]

在 2026/2/23 11:58, Yu Kuai 写道:

> Set chunk_sectors to the full stripe width (io_opt) so that the block
> layer splits I/O at full stripe boundaries. This ensures that large
> writes are aligned to full stripes, avoiding the read-modify-write
> overhead that occurs with partial stripe writes in RAID-5/6.
>
> When chunk_sectors is set, the block layer's bio splitting logic in
> get_max_io_size() uses blk_boundary_sectors_left() to limit I/O size
> to the boundary. This naturally aligns split bios to full stripe
> boundaries, enabling more efficient full stripe writes.
>
> Test results with 24-disk RAID5 (chunk_size=64k):
>    dd if=/dev/zero of=/dev/md0 bs=10M oflag=direct
>    Before: 461 MB/s
>    After:  520 MB/s  (+12.8%)
>
> Suggested-by: Christoph Hellwig<hch@xxxxxxxxxxxxx>
> Signed-off-by: Yu Kuai<yukuai@xxxxxxxxx>
> ---
>   drivers/md/raid5.c | 1 +
>   1 file changed, 1 insertion(+)

Applied to md-7.0

-- 
Thansk,
Kuai