Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
Mime-Version: 1.0
Subject: RE: [RFC PATCH v2 4/5] scsi: ufs: L2P map management for HPB read
Reply-To: daejun7.park@samsung.com
From:   Daejun Park <daejun7.park@samsung.com>
To:     Avri Altman <Avri.Altman@wdc.com>,
        Daejun Park <daejun7.park@samsung.com>,
        ALIM AKHTAR <alim.akhtar@samsung.com>,
        "jejb@linux.ibm.com" <jejb@linux.ibm.com>,
        "martin.petersen@oracle.com" <martin.petersen@oracle.com>,
        "asutoshd@codeaurora.org" <asutoshd@codeaurora.org>,
        "beanhuo@micron.com" <beanhuo@micron.com>,
        "stanley.chu@mediatek.com" <stanley.chu@mediatek.com>,
        "cang@codeaurora.org" <cang@codeaurora.org>,
        "bvanassche@acm.org" <bvanassche@acm.org>,
        "tomas.winkler@intel.com" <tomas.winkler@intel.com>
CC:     "linux-scsi@vger.kernel.org" <linux-scsi@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Sang-yoon Oh <sangyoon.oh@samsung.com>,
        Sung-Jun Park <sungjun07.park@samsung.com>,
        yongmyung lee <ymhungry.lee@samsung.com>,
        Jinyoung CHOI <j-young.choi@samsung.com>,
        Adel Choi <adel.choi@samsung.com>,
        BoRam Shin <boram.shin@samsung.com>
In-Reply-To: <SN6PR04MB4640114902AEFE69CCC54C01FC9A0@SN6PR04MB4640.namprd04.prod.outlook.com>
Message-ID: <1210830415.21592444702291.JavaMail.epsvc@epcpadp1>
Date:   Thu, 18 Jun 2020 10:03:45 +0900
Content-Transfer-Encoding: 7bit
Content-Type: text/plain; charset="utf-8"
References: <SN6PR04MB4640114902AEFE69CCC54C01FC9A0@SN6PR04MB4640.namprd04.prod.outlook.com>
        <231786897.01592213402355.JavaMail.epsvc@epcpadp1>
        <231786897.01592212081335.JavaMail.epsvc@epcpadp2>
        <336371513.41592205783606.JavaMail.epsvc@epcpadp2>
        <231786897.01592205482200.JavaMail.epsvc@epcpadp2>
        <231786897.01592214002170.JavaMail.epsvc@epcpadp1>
        <CGME20200615062708epcms2p19a7fbc051bcd5e843c29dcd58fff4210@epcms2p6>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

> +
> > +static struct ufshpb_map_ctx *ufshpb_get_map_ctx(struct ufshpb_lu *hpb)
> > +{
> > +       struct ufshpb_map_ctx *mctx;
> > +       int i, j;
> > +
> > +       mctx = mempool_alloc(ufshpb_drv.ufshpb_mctx_pool, GFP_KERNEL);
> > +       if (!mctx)
> > +               return NULL;
> So you use ufshpb_host_map_kbytes as the min_nr in your mempool_create,
> But you know that you need max_lru_active_cnt x srgns_per_rgn such mapping context elements.
> So you are
> a) failing to provide the slab allocator an information that you already have, and
> b) selecting from a finite pool will assure that you'll never exceed max-active-regions,
>    even if some corner case fails your logic.
It was intend to provide user-configurable pre-allocated memory to reduce
latency due to memory allocation. The value of ufshpb_host_map_kbytes can
be set to max_lru_active_cnt x srgns_per_rgn, if the user want to.

Thanks,
Daejun