Re: [PATCH v1 0/4] btrfs: read_policy types latency, device and round-robin

Josef Bacik
2020-10-28T22:26:25Z

On 10/28/20 9:25 AM, Anand Jain wrote:
> Based on misc-next
>
> Depends on the following 3 patches in the mailing list.
> btrfs: add btrfs_strmatch helper
> btrfs: create read policy framework
> btrfs: create read policy sysfs attribute, pid
>
> v1:
> Drop tracing patch
> Drop factoring inflight command
> Here below is the performance differences, when inflight is used, it pushed
> few commands to the other device, so losing the potential merges.
>
> with inflight:
> READ: bw=195MiB/s (204MB/s), 195MiB/s-195MiB/s (204MB/s-204MB/s), io=15.6GiB (16.8GB), run=82203-82203msec
> sda 256054
> sdc 20
>
> without inflight:
> READ: bw=192MiB/s (202MB/s), 192MiB/s-192MiB/s (202MB/s-202MB/s), io=15.6GiB (16.8GB), run=83231-83231msec
> sda 141006
> sdc 0
>

What's the baseline? I think 3mib/s is not that big of a tradeoff for
complexity, but if baseline is like 190mib/s then maybe its worth it. If
baseline is 90mib/s then I say it's not worth the inflight. Thanks,

Josef