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From: Guoqing Jiang <guoqing.jiang@cloud.ionos.com>
To: Ming Lei <ming.lei@redhat.com>
Cc: axboe@kernel.dk, linux-block@vger.kernel.org,
	Philipp Reisner <philipp.reisner@linbit.com>,
	Lars Ellenberg <lars.ellenberg@linbit.com>,
	drbd-dev@lists.linbit.com
Subject: Re: [PATCH RFC 1/5] block: return ns precision from disk_start_io_acct
Date: Wed, 8 Jul 2020 19:46:39 +0200	[thread overview]
Message-ID: <1796891f-66c3-09c4-559f-15d1d350d817@cloud.ionos.com> (raw)
In-Reply-To: <ad89a0b2-3b40-b515-2120-85bc0274165b@cloud.ionos.com>

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

  reply	other threads:[~2020-07-08 17:46 UTC|newest]

Thread overview: 22+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-07-08  7:58 [RFC PATCH 0/4] block: add two statistic tables Guoqing Jiang
2020-07-08  7:58 ` [PATCH RFC 1/5] block: return ns precision from disk_start_io_acct Guoqing Jiang
2020-07-08 13:27   ` Ming Lei
2020-07-08 13:53     ` Guoqing Jiang
2020-07-08 17:46       ` Guoqing Jiang [this message]
2020-07-08  7:58 ` [PATCH RFC 2/5] drbd: remove unused argument from drbd_request_prepare and __drbd_make_request Guoqing Jiang
2020-07-08  7:58 ` [PATCH RFC 3/5] drbd: rename start_jif to start_ns Guoqing Jiang
2020-07-08  7:58 ` [PATCH RFC 4/5] block: add a statistic table for io latency Guoqing Jiang
2020-07-08 13:29   ` Ming Lei
2020-07-08 14:02     ` Guoqing Jiang
2020-07-08 14:06       ` Guoqing Jiang
2020-07-09 18:48         ` Guoqing Jiang
2020-07-10  0:53           ` Ming Lei
2020-07-10  8:55             ` Guoqing Jiang
2020-07-10 10:00               ` Ming Lei
2020-07-10 10:29                 ` Guoqing Jiang
2020-07-11  1:32                   ` Ming Lei
2020-07-12 20:39                     ` Guoqing Jiang
2020-07-12 20:44                       ` Jens Axboe
2020-07-12 21:04                         ` Guoqing Jiang
2020-07-10 14:04               ` Jens Axboe
2020-07-08  7:58 ` [PATCH RFC 5/5] block: add a statistic table for io sector Guoqing Jiang

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