From: Bart Van Assche <bvanassche@acm.org>
To: "Ziqi Chen" <quic_ziqichen@quicinc.com>,
"Peter Wang (王信友)" <peter.wang@mediatek.com>,
"quic_rampraka@quicinc.com" <quic_rampraka@quicinc.com>,
"quic_nguyenb@quicinc.com" <quic_nguyenb@quicinc.com>,
"quic_nitirawa@quicinc.com" <quic_nitirawa@quicinc.com>,
"beanhuo@micron.com" <beanhuo@micron.com>,
"avri.altman@wdc.com" <avri.altman@wdc.com>,
"martin.petersen@oracle.com" <martin.petersen@oracle.com>,
"junwoo80.lee@samsung.com" <junwoo80.lee@samsung.com>,
"mani@kernel.org" <mani@kernel.org>,
"quic_cang@quicinc.com" <quic_cang@quicinc.com>
Cc: "linux-scsi@vger.kernel.org" <linux-scsi@vger.kernel.org>,
"alim.akhtar@samsung.com" <alim.akhtar@samsung.com>,
"jejb@linux.ibm.com" <jejb@linux.ibm.com>,
"quic_asutoshd@quicinc.com" <quic_asutoshd@quicinc.com>,
"quic_mnaresh@quicinc.com" <quic_mnaresh@quicinc.com>,
"manivannan.sadhasivam@linaro.org"
<manivannan.sadhasivam@linaro.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] scsi: ufs: core: quiesce request queues before check pending cmds
Date: Wed, 26 Jun 2024 09:33:33 -0700 [thread overview]
Message-ID: <d1768030-28fe-476b-9161-2b26f296c0dd@acm.org> (raw)
In-Reply-To: <272184ed-2fd8-413a-816c-9470bf9332da@quicinc.com>
On 6/26/24 6:18 AM, Ziqi Chen wrote:
> On 6/26/2024 12:13 AM, Bart Van Assche wrote:
>> ufshcd_wait_for_doorbell_clr() should be removed and
>> ufshcd_clock_scaling_prepare() should use blk_mq_freeze_*().
>> See also my patch "ufs: Simplify the clock scaling mechanism
>> implementation" from 5 years ago
>> (https://lore.kernel.org/linux-scsi/20191112173743.141503-5-bvanassche@acm.org/).
>
> The defect of blk_mq_freeze_*() is that it would bring in significant
> latency and performance regression. I don't think it is what many people
> want to see.
This can be solved by inserting a synchronize_srcu_expedited() call
between the blk_freeze_queue_start() and the
blk_mq_freeze_queue_wait_timeout() calls. With that call added, the
latency of the new code should be lower than that of the
io_schedule_timeout(msecs_to_jiffies(20)) call in the current code.
blk_mq_freeze_*() is only slow if the RCU grace period is not expedited.
Bart.
prev parent reply other threads:[~2024-06-26 16:33 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-06-07 10:06 Ziqi Chen
2024-06-07 12:33 ` Bart Van Assche
2024-06-11 11:02 ` Ziqi Chen
2024-06-11 13:51 ` Bart Van Assche
2024-06-12 6:07 ` Ziqi Chen
2024-06-11 13:54 ` Bart Van Assche
2024-06-20 20:57 ` Bart Van Assche
2024-06-24 9:56 ` Ziqi Chen
2024-06-24 16:29 ` Bart Van Assche
2024-06-25 3:38 ` Peter Wang (王信友)
2024-06-25 16:13 ` Bart Van Assche
2024-06-26 3:52 ` Peter Wang (王信友)
2024-06-26 13:18 ` Ziqi Chen
2024-06-26 16:33 ` Bart Van Assche [this message]
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