linux-kernel - Re: [PATCH RFC] scsi: core: remove unsed 'restarts' from scsi

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Date:   Mon, 28 Nov 2022 10:26:37 +0800
From:   Jason Yan <yanaijie@...wei.com>
To:     Yu Kuai <yukuai1@...weicloud.com>, <ming.lei@...hat.com>,
        <jejb@...ux.ibm.com>, <martin.petersen@...cle.com>
CC:     <linux-scsi@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <yi.zhang@...wei.com>, "yukuai (C)" <yukuai3@...wei.com>
Subject: Re: [PATCH RFC] scsi: core: remove unsed 'restarts' from scsi_device

On 2022/11/26 16:54, Yu Kuai wrote:
> Hi,
> 
> 在 2022/11/18 19:30, Yu Kuai 写道:
>> From: Yu Kuai <yukuai3@...wei.com>
>>
>> During code review, I found that 'restarts' is not useful anymore after
>> the following commits:
>>
>> 1) commit ab3cee3762e5 ("blk-mq: In blk_mq_dispatch_rq_list() "no budget"
>> is a reason to kick")
>> 2) commit d3b38596875d ("blk-mq: run queue no matter whether the request
>> is the last request")
>> 3) commit 673235f91531 ("scsi: core: Fix race between handling 
>> STS_RESOURCE
>> and completion")
>>
>> Now that if get budget ever failed, block layer will make sure to
>> trigger new run queue for the hctx. Hence there is no need to run queue
>> from scsi layer in this case.
>>
> 
> Does anyone has suggestions about this patch?
> 
> More info why I tried to remove this:
> 
> while testing megaraid with 4 nvme with none elevator, the default
> queue_depth is 128, while I test it with fio 128 jobs and 1 iodepth,
> bw is about 4Gib/s, however, if I test with 128 jobs and 2 iodepth,
> bw is decreased to about 0.8Gib/s, and with this patch applied,
> bw can stay 4Gib/s in the later case.
> 

Hi Yu Kuai,

This information should be included in the commit message.

Thanks,
Jason