linux-kernel - RE: [RFC PATCH v3 0/5] scsi: ufs: Add Host Performance Booster Support

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Message-ID: <SN6PR04MB46402436A9E1FFE70967C444FC6E0@SN6PR04MB4640.namprd04.prod.outlook.com>
Date:   Mon, 29 Jun 2020 11:06:29 +0000
From:   Avri Altman <Avri.Altman@....com>
To:     Bean Huo <huobean@...il.com>,
        "daejun7.park@...sung.com" <daejun7.park@...sung.com>,
        "jejb@...ux.ibm.com" <jejb@...ux.ibm.com>,
        "martin.petersen@...cle.com" <martin.petersen@...cle.com>,
        "asutoshd@...eaurora.org" <asutoshd@...eaurora.org>,
        "stanley.chu@...iatek.com" <stanley.chu@...iatek.com>,
        "cang@...eaurora.org" <cang@...eaurora.org>,
        "bvanassche@....org" <bvanassche@....org>,
        "tomas.winkler@...el.com" <tomas.winkler@...el.com>,
        ALIM AKHTAR <alim.akhtar@...sung.com>
CC:     "linux-scsi@...r.kernel.org" <linux-scsi@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Sang-yoon Oh <sangyoon.oh@...sung.com>,
        Sung-Jun Park <sungjun07.park@...sung.com>,
        yongmyung lee <ymhungry.lee@...sung.com>,
        Jinyoung CHOI <j-young.choi@...sung.com>,
        Adel Choi <adel.choi@...sung.com>,
        BoRam Shin <boram.shin@...sung.com>
Subject: RE: [RFC PATCH v3 0/5] scsi: ufs: Add Host Performance Booster
 Support



> 
> Hi Avri
> 
> On Mon, 2020-06-29 at 05:24 +0000, Avri Altman wrote:
> > Hi Bean,
> > >
> > > Hi Daejun
> > >
> > > Seems you intentionally ignored to give you comments on my
> > > suggestion.
> > > let me provide the reason.
> > >
> > > Before submitting your next version patch, please check your L2P
> > > mapping HPB reqeust submission logical algorithem. I have did
> > > performance comparison testing on 4KB, there are about 13%
> > > performance
> > > drop. Also the hit count is lower. I don't know if this is related
> > > to
> > > your current work queue scheduling, since you didn't add the timer
> > > for
> > > each HPB request.
> >
> > In device control mode, the various decisions,
> > and specifically those that are causing repetitive evictions,
> > are made by the device.
> > Is this the issue that you are referring to?
> >
> 
> For this device mode, if HPB mapping table of the active region becomes
> dirty in the UFS device side, there is repetitive inactive rsp, but it
> is not the reason for the condition I mentioned here.
> 
> > As for the driver, do you see any issue that is causing unnecessary
> > latency?
> >
> 
> In Daejun's patch, it now uses work_queue, and as long there is new RSP of
> thesubregion to be activated, the driver will queue "work" to this work
> queue, actually, this is deferred work. we don't know when it will be
> scheduled/finished. we need to optimize it.
But those "to-do" lists are checked on every completion interrupt and on every resume.
Do you see any scenario in which the "to-be-activated" or "to-be-inactivate" work is getting starved?