linux-kernel - RE: [PATCH 3/8] scsi: ufshpb: Add region's reads counter

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Date:   Mon, 01 Feb 2021 12:51:36 +0900
From:   Daejun Park <daejun7.park@...sung.com>
To:     "James E . J . Bottomley" <jejb@...ux.vnet.ibm.com>,
        "Martin K . Petersen" <martin.petersen@...cle.com>,
        "linux-scsi@...r.kernel.org" <linux-scsi@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
CC:     "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        Bart Van Assche <bvanassche@....org>,
        yongmyung lee <ymhungry.lee@...sung.com>,
        Daejun Park <daejun7.park@...sung.com>,
        ALIM AKHTAR <alim.akhtar@...sung.com>,
        "asutoshd@...eaurora.org" <asutoshd@...eaurora.org>,
        Zang Leigang <zangleigang@...ilicon.com>,
        Avi Shchislowski <avi.shchislowski@....com>,
        Bean Huo <beanhuo@...ron.com>,
        "cang@...eaurora.org" <cang@...eaurora.org>,
        "stanley.chu@...iatek.com" <stanley.chu@...iatek.com>,
        Avri Altman <avri.altman@....com>
Subject: RE: [PATCH 3/8] scsi: ufshpb: Add region's reads counter

Hi Avri,

Thanks for adding HCM support on HPB.
I have some opinion for this patch.

> +#define WORK_PENDING 0
> +#define ACTIVATION_THRSHLD 4 /* 4 IOs */
Rather than fixing it with macro, how about using sysfs and make it
configurable?

> @@ -306,12 +325,39 @@ void ufshpb_prep(struct ufs_hba *hba, struct ufshcd_lrb *lrbp)
>  		ufshpb_set_ppn_dirty(hpb, rgn_idx, srgn_idx, srgn_offset,
>  				 transfer_len);
>  		spin_unlock_irqrestore(&hpb->rgn_state_lock, flags);
> +
> +		if (ufshpb_mode == HPB_HOST_CONTROL)
> +			atomic64_set(&rgn->reads, 0);
> +
>  		return;
>  	}
>  
> +	if (ufshpb_mode == HPB_HOST_CONTROL)
> +		reads = atomic64_inc_return(&rgn->reads);
> +
>  	if (!ufshpb_is_support_chunk(transfer_len))
>  		return; <- *this*
>  
> +	if (ufshpb_mode == HPB_HOST_CONTROL) {
> +		/*
> +		 * in host control mode, reads are the main source for
> +		 * activation trials.
> +		 */
> +		if (reads == ACTIVATION_THRSHLD) {
If the chunk size is not supported, we can not active this region
permanently. It may be returned before get this statement.

> diff --git a/drivers/scsi/ufs/ufshpb.h b/drivers/scsi/ufs/ufshpb.h
> index 8a34b0f42754..b0e78728af38 100644
> --- a/drivers/scsi/ufs/ufshpb.h
> +++ b/drivers/scsi/ufs/ufshpb.h
> @@ -115,6 +115,9 @@ struct ufshpb_region {
>  	/* below information is used by lru */
>  	struct list_head list_lru_rgn;
>  	unsigned long rgn_flags;
> +
> +	/* region reads - for host mode */
> +	atomic64_t reads;
I think 32 bits are suitable, because it is normalized by worker on every
specific time.

Thanks,
Daejun