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.
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
