Re: [PATCH v2 18/20] scsi: ufs: Optimize the command queueing code

From: "Asutosh Das (asd)" <asutoshd@codeaurora.org>
To: Bart Van Assche <bvanassche@acm.org>,
	"Martin K . Petersen" <martin.petersen@oracle.com>
Cc: Jaegeuk Kim <jaegeuk@kernel.org>,
	Adrian Hunter <adrian.hunter@intel.com>,
	linux-scsi@vger.kernel.org,
	"James E.J. Bottomley" <jejb@linux.ibm.com>,
	Bean Huo <beanhuo@micron.com>, Can Guo <cang@codeaurora.org>,
	Avri Altman <avri.altman@wdc.com>,
	Stanley Chu <stanley.chu@mediatek.com>,
	Keoseong Park <keosung.park@samsung.com>
Subject: Re: [PATCH v2 18/20] scsi: ufs: Optimize the command queueing code
Date: Mon, 22 Nov 2021 15:02:02 -0800	[thread overview]
Message-ID: <2071f69b-885f-e0c5-3ded-9f0c39eb38ae@codeaurora.org> (raw)
In-Reply-To: <f6eb1b4c-ef73-7e34-cecd-fa0c9ce07a2f@acm.org>

On 11/22/2021 10:13 AM, Bart Van Assche wrote:
> On 11/22/21 9:46 AM, Asutosh Das (asd) wrote:
>> On 11/19/2021 11:57 AM, Bart Van Assche wrote:
>>> +    blk_freeze_queue_start(hba->tmf_queue);
>>> +    blk_freeze_queue_start(hba->cmd_queue);
>>> +    shost_for_each_device(sdev, hba->host)
>>> +        blk_freeze_queue_start(sdev->request_queue);
>>
>> This would still issue the requests present in the queue before 
>> freezing and that's a concern.
> 
> Isn't that exactly what the existing code is doing since the existing 
> code waits until both doorbell registers are zero? See also 
> ufshcd_wait_for_doorbell_clr().
> 
> Thanks,
> 
> Bart.
Current code waits for the already issued requests to complete. It 
doesn't issue the yet-to-be issued requests. Wouldn't freezing the queue 
issue the requests in the context of scaling_{up/down}?
If yes, I don't think the current code is doing that.

-asd

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