[Drbd-dev] [PATCH RFC 1/5] block: return ns precision from disk_start_io_acct

[Guoqing Jiang]

On 7/8/20 3:53 PM, Guoqing Jiang wrote:
>>
>> Cost of ktime_get_ns() can be observed as not cheap in high IOPS device,
>
> Could you share some links about it? Thanks.
>
>> so not sure the conversion is good. Also could you share what benefit 
>> we can
>> get with this change?
>
> Without the conversion, we have to track io latency with jiffies in 
> 4th patch.
> Then with HZ=100, some rows (such as 1ms, 2ms and 4ms) in that table
> don't make sense. 

Hmm, I can still output those rows based on HZ_TO_MSEC_NUM, which means
this patch can be dropped since the cost of ktime_get_ns is more expensive.

Thanks,
Guoqing