Hi Song,
Any thoughts on this?
On 1/17/2023 5:53 PM, Jonathan Derrick wrote:
> From: Jon Derrick <jonathan.derrick@xxxxxxxxx>
>
> If the bitmap space has enough room, size the I/O for the last bitmap
> page write to the optimal I/O size for the storage device. The expanded
> write is checked that it won't overrun the data or metadata.
>
> This change helps increase performance by preventing unnecessary
> device-side read-mod-writes due to non-atomic write unit sizes.
>
> Ex biosnoop log. Device lba size 512, optimal size 4k:
> Before:
> Time Process PID Device LBA Size Lat
> 0.843734 md0_raid10 5267 nvme0n1 W 24 3584 1.17
> 0.843933 md0_raid10 5267 nvme1n1 W 24 3584 1.36
> 0.843968 md0_raid10 5267 nvme1n1 W 14207939968 4096 0.01
> 0.843979 md0_raid10 5267 nvme0n1 W 14207939968 4096 0.02
>
> After:
> Time Process PID Device LBA Size Lat
> 18.374244 md0_raid10 6559 nvme0n1 W 24 4096 0.01
> 18.374253 md0_raid10 6559 nvme1n1 W 24 4096 0.01
> 18.374300 md0_raid10 6559 nvme0n1 W 11020272296 4096 0.01
> 18.374306 md0_raid10 6559 nvme1n1 W 11020272296 4096 0.02
>
> Signed-off-by: Jon Derrick <jonathan.derrick@xxxxxxxxx>
> ---
> drivers/md/md-bitmap.c | 27 ++++++++++++++++++---------
> 1 file changed, 18 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/md/md-bitmap.c b/drivers/md/md-bitmap.c
> index e7cc6ba1b657..569297ea9b99 100644
> --- a/drivers/md/md-bitmap.c
> +++ b/drivers/md/md-bitmap.c
> @@ -220,6 +220,7 @@ static int write_sb_page(struct bitmap *bitmap, struct page *page, int wait)
> rdev = NULL;
> while ((rdev = next_active_rdev(rdev, mddev)) != NULL) {
> int size = PAGE_SIZE;
> + int optimal_size = PAGE_SIZE;
> loff_t offset = mddev->bitmap_info.offset;
>
> bdev = (rdev->meta_bdev) ? rdev->meta_bdev : rdev->bdev;
> @@ -228,9 +229,14 @@ static int write_sb_page(struct bitmap *bitmap, struct page *page, int wait)
> int last_page_size = store->bytes & (PAGE_SIZE-1);
> if (last_page_size == 0)
> last_page_size = PAGE_SIZE;
> - size = roundup(last_page_size,
> - bdev_logical_block_size(bdev));
> + size = roundup(last_page_size, bdev_logical_block_size(bdev));
> + if (bdev_io_opt(bdev) > bdev_logical_block_size(bdev))
> + optimal_size = roundup(last_page_size, bdev_io_opt(bdev));
> + else
> + optimal_size = size;
> }
> +
> +
> /* Just make sure we aren't corrupting data or
> * metadata
> */
> @@ -246,9 +252,11 @@ static int write_sb_page(struct bitmap *bitmap, struct page *page, int wait)
> goto bad_alignment;
> } else if (offset < 0) {
> /* DATA BITMAP METADATA */
> - if (offset
> - + (long)(page->index * (PAGE_SIZE/512))
> - + size/512 > 0)
> + loff_t off = offset + (long)(page->index * (PAGE_SIZE/512));
> + if (size != optimal_size &&
> + off + optimal_size/512 <= 0)
> + size = optimal_size;
> + else if (off + size/512 > 0)
> /* bitmap runs in to metadata */
> goto bad_alignment;
> if (rdev->data_offset + mddev->dev_sectors
> @@ -257,10 +265,11 @@ static int write_sb_page(struct bitmap *bitmap, struct page *page, int wait)
> goto bad_alignment;
> } else if (rdev->sb_start < rdev->data_offset) {
> /* METADATA BITMAP DATA */
> - if (rdev->sb_start
> - + offset
> - + page->index*(PAGE_SIZE/512) + size/512
> - > rdev->data_offset)
> + loff_t off = rdev->sb_start + offset + page->index*(PAGE_SIZE/512);
> + if (size != optimal_size &&
> + off + optimal_size/512 <= rdev->data_offset)
> + size = optimal_size;
> + else if (off + size/512 > rdev->data_offset)
> /* bitmap runs in to data */
> goto bad_alignment;
> } else {
