On Thu, Feb 16, 2023 at 3:52 PM Jonathan Derrick
[off-list ref] wrote:

On 2/10/2023 10:32 AM, Song Liu wrote:

quoted

Hi Jonathan,

On Thu, Feb 9, 2023 at 12:38 PM Jonathan Derrick
[off-list ref] wrote:

quoted

Hi Song,

Any thoughts on this?

I am really sorry that I missed this patch.

quoted

On 1/17/2023 5:53 PM, Jonathan Derrick wrote:

quoted

From: Jon Derrick <jonathan.derrick@linux.dev>

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

Do we see significant improvements from io benchmarks?

Yes. With lbaf=512, optimal i/o size=4k:

Without patch:
  write: IOPS=1570, BW=6283KiB/s (6434kB/s)(368MiB/60001msec); 0 zone resets
With patch:
  write: IOPS=59.7k, BW=233MiB/s (245MB/s)(13.7GiB/60001msec); 0 zone resets

The difference is much bigger than I expected. Given this big improvements, I
think we should ship this improvement. Unfortunately, we are too late for 6.3.
Let's plan to ship this in the 6.4 release. I am on vacation this
week. I will work
on this afterwards.

Thanks,
Song