RE: [PATCH v4 7/9] scsi: ufshpb: Add "Cold" regions timer

From: Avri Altman <Avri.Altman@wdc.com>
To: "daejun7.park@samsung.com" <daejun7.park@samsung.com>,
	"James E . J . Bottomley" <jejb@linux.vnet.ibm.com>,
	"Martin K . Petersen" <martin.petersen@oracle.com>,
	"linux-scsi@vger.kernel.org" <linux-scsi@vger.kernel.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Cc: "gregkh@linuxfoundation.org" <gregkh@linuxfoundation.org>,
	Bart Van Assche <bvanassche@acm.org>,
	yongmyung lee <ymhungry.lee@samsung.com>,
	ALIM AKHTAR <alim.akhtar@samsung.com>,
	"asutoshd@codeaurora.org" <asutoshd@codeaurora.org>,
	Zang Leigang <zangleigang@hisilicon.com>,
	Avi Shchislowski <Avi.Shchislowski@wdc.com>,
	Bean Huo <beanhuo@micron.com>,
	"cang@codeaurora.org" <cang@codeaurora.org>,
	"stanley.chu@mediatek.com" <stanley.chu@mediatek.com>
Subject: RE: [PATCH v4 7/9] scsi: ufshpb: Add "Cold" regions timer
Date: Tue, 2 Mar 2021 08:45:20 +0000	[thread overview]
Message-ID: <DM6PR04MB657580F9080C31AB5AED1FDBFC999@DM6PR04MB6575.namprd04.prod.outlook.com> (raw)
In-Reply-To: <878274034.81614673683390.JavaMail.epsvc@epcpadp4>

> 
> Hi Avri,
> 
> > +static void ufshpb_read_to_handler(struct work_struct *work)
> > +{
> > +        struct delayed_work *dwork = to_delayed_work(work);
> > +        struct ufshpb_lu *hpb;
> > +        struct victim_select_info *lru_info;
> > +        struct ufshpb_region *rgn;
> > +        unsigned long flags;
> > +        LIST_HEAD(expired_list);
> > +
> > +        hpb = container_of(dwork, struct ufshpb_lu, ufshpb_read_to_work);
> > +
> > +        if (test_and_set_bit(TIMEOUT_WORK_PENDING, &hpb-
> >work_data_bits))
> > +                return;
> > +
> > +        spin_lock_irqsave(&hpb->rgn_state_lock, flags);
> > +
> > +        lru_info = &hpb->lru_info;
> > +
> > +        list_for_each_entry(rgn, &lru_info->lh_lru_rgn, list_lru_rgn) {
> > +                bool timedout = ktime_after(ktime_get(), rgn->read_timeout);
> > +
> > +                if (timedout) {
> 
> It is important not just to check the timeout, but how much time has passed.
> If the time exceeded is twice the threshold, the read_timeout_expiries
> value should be reduced by 2 instead of 1.
Theoretically this shouldn't happened.
Please note that POLLING_INTERVAL_MS << READ_TO_MS.
Better add appropriate check when making those configurable.

Thanks,
Avri
> 
> > +                        rgn->read_timeout_expiries--;
> 
> Thanks,
> Daejun