On Sat, Feb 18, 2023 at 2:36 AM Jonathan Derrick
<jonathan.derrick@xxxxxxxxx> 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.
Hi Jonathan
Thanks for your patch.
Could you explain more about the how the optimal io size can affect
the device-side read-mod-writes?
Regards
Xiao
>
> Example Intel/Solidigm P5520
> Raid10, Chunk-size 64M, bitmap-size 57228 bits
>
> $ mdadm --create /dev/md0 --level=10 --raid-devices=4 /dev/nvme{0,1,2,3}n1 --assume-clean --bitmap=internal --bitmap-chunk=64M
> $ fio --name=test --direct=1 --filename=/dev/md0 --rw=randwrite --bs=4k --runtime=60
>
> Without patch:
> write: IOPS=1676, BW=6708KiB/s (6869kB/s)(393MiB/60001msec); 0 zone resets
>
> With patch:
> write: IOPS=15.7k, BW=61.4MiB/s (64.4MB/s)(3683MiB/60001msec); 0 zone resets
>
> Biosnoop:
> Without patch:
> Time Process PID Device LBA Size Lat
> 1.410377 md0_raid10 6900 nvme0n1 W 16 4096 0.02
> 1.410387 md0_raid10 6900 nvme2n1 W 16 4096 0.02
> 1.410374 md0_raid10 6900 nvme3n1 W 16 4096 0.01
> 1.410381 md0_raid10 6900 nvme1n1 W 16 4096 0.02
> 1.410411 md0_raid10 6900 nvme1n1 W 115346512 4096 0.01
> 1.410418 md0_raid10 6900 nvme0n1 W 115346512 4096 0.02
> 1.410915 md0_raid10 6900 nvme2n1 W 24 3584 0.43
> 1.410935 md0_raid10 6900 nvme3n1 W 24 3584 0.45
> 1.411124 md0_raid10 6900 nvme1n1 W 24 3584 0.64
> 1.411147 md0_raid10 6900 nvme0n1 W 24 3584 0.66
> 1.411176 md0_raid10 6900 nvme3n1 W 2019022184 4096 0.01
> 1.411189 md0_raid10 6900 nvme2n1 W 2019022184 4096 0.02
>
> With patch:
> Time Process PID Device LBA Size Lat
> 5.747193 md0_raid10 727 nvme0n1 W 16 4096 0.01
> 5.747192 md0_raid10 727 nvme1n1 W 16 4096 0.02
> 5.747195 md0_raid10 727 nvme3n1 W 16 4096 0.01
> 5.747202 md0_raid10 727 nvme2n1 W 16 4096 0.02
> 5.747229 md0_raid10 727 nvme3n1 W 1196223704 4096 0.02
> 5.747224 md0_raid10 727 nvme0n1 W 1196223704 4096 0.01
> 5.747279 md0_raid10 727 nvme0n1 W 24 4096 0.01
> 5.747279 md0_raid10 727 nvme1n1 W 24 4096 0.02
> 5.747284 md0_raid10 727 nvme3n1 W 24 4096 0.02
> 5.747291 md0_raid10 727 nvme2n1 W 24 4096 0.02
> 5.747314 md0_raid10 727 nvme2n1 W 2234636712 4096 0.01
> 5.747317 md0_raid10 727 nvme1n1 W 2234636712 4096 0.02
>
> Signed-off-by: Jon Derrick <jonathan.derrick@xxxxxxxxx>
> ---
> v1->v2: Add more information to commit message
>
> 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 {
> --
> 2.27.0
>
