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From: Yu Kuai <yukuai1@huaweicloud.com>
To: Bart Van Assche <bvanassche@acm.org>,
	Yu Kuai <yukuai1@huaweicloud.com>,
	Christoph Hellwig <hch@infradead.org>
Cc: Ed Tsai <ed.tsai@mediatek.com>,
	axboe@kernel.dk, linux-block@vger.kernel.org,
	linux-scsi@vger.kernel.org, linux-kernel@vger.kernel.org,
	martin.petersen@oracle.com, stanley.chu@mediatek.com,
	peter.wang@mediatek.com, chun-hung.wu@mediatek.com,
	alice.chao@mediatek.com, powen.kao@mediatek.com,
	naomi.chu@mediatek.com, wsd_upstream@mediatek.com,
	"yukuai (C)" <yukuai3@huawei.com>
Subject: Re: [PATCH 2/2] ufs: don't use the fair tag sharings
Date: Thu, 18 May 2023 09:49:06 +0800	[thread overview]
Message-ID: <f9ccab59-91a1-69d5-6d20-2c6ea0e24b5a@huaweicloud.com> (raw)
In-Reply-To: <097caed2-10b3-7cd1-7c06-90f983e5c720@acm.org>

Hi,

在 2023/05/18 2:23, Bart Van Assche 写道:
> On 5/17/23 00:49, Yu Kuai wrote:
>> 在 2023/05/16 23:12, Bart Van Assche 写道:
>>> I propose that we switch to one of these two approaches:
>>
>> How about a smoothing method that the device with more io will share
>> more tag, and each device will get at least one tag?
> 
> Hi Yu,
> 
> hctx_may_queue() is called from the hot path (blk_mq_get_tag()). I'm 
> pretty sure that adding any nontrivial code in that path will cause a 
> performance (IOPS) regression. So I don't think that adding a smoothing 
> method in hctx_may_queue() is a realistic option.
> 

Currently, fair share from hctx_may_queue() requires two
atomic_read(active_queues and active_requests), I think this smoothing
method can be placed into get_tag fail path, for example, the more times
a disk failed to get tag in a period of time, the more tag this disk can
get, and all the information can be updated here(perhaps directly
record how many tags a disk can get, then hctx_may_queue() still only
require 2 atomic_read()).

Thanks,
Bart


  reply	other threads:[~2023-05-18  1:49 UTC|newest]

Thread overview: 26+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-05-09  6:52 [PATCH 0/2] block: improve the share tag set performance Ed Tsai
2023-05-09  6:52 ` [PATCH 1/2] block: make the fair sharing of tag configurable Ed Tsai
2023-05-09 21:33   ` kernel test robot
2023-05-11 15:33   ` Christoph Hellwig
2023-05-22  5:30   ` kernel test robot
2023-05-09  6:52 ` [PATCH 2/2] ufs: don't use the fair tag sharings Ed Tsai
2023-05-09  8:03   ` Avri Altman
2023-05-09 14:04     ` Bart Van Assche
2023-05-09 16:19       ` Avri Altman
2023-05-09 16:30         ` Bart Van Assche
2023-05-10  5:21           ` Avri Altman
2023-05-10 15:56             ` Bart Van Assche
2023-05-11 15:34   ` Christoph Hellwig
2023-05-11 15:38     ` Bart Van Assche
2023-05-12 14:02       ` Christoph Hellwig
2023-05-12 18:12         ` Bart Van Assche
2023-05-13  3:09           ` Yu Kuai
2023-05-16 15:12             ` Bart Van Assche
2023-05-17  7:49               ` Yu Kuai
2023-05-17 18:23                 ` Bart Van Assche
2023-05-18  1:49                   ` Yu Kuai [this message]
2023-05-18  2:23                     ` Bart Van Assche
2023-05-18  7:55                       ` Yu Kuai
2023-06-13 14:07                         ` Bart Van Assche
2023-06-14  1:58                           ` Yu Kuai
2023-05-10 22:56 ` [PATCH 0/2] block: improve the share tag set performance Bart Van Assche

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