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

Anand Jain
2020-10-29T01:11:48Z

On 28/10/20 10:32 pm, Josef Bacik wrote:
> 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,

Oh no I have to rerun the test cases here. As far as I remember
without inflight was better than with inflight. Because with
inflight there were fewer merges leading to more read IOs.

Will rerun and send the data.

Thanks, Anand

>
> Josef