linux-kernel - Re: [PATCH v29 4/4] scsi: ufs: Add HPB 2.0 support

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Date:   Mon, 15 Mar 2021 13:05:53 +0800
From:   Can Guo <cang@...eaurora.org>
To:     daejun7.park@...sung.com
Cc:     Greg KH <gregkh@...uxfoundation.org>, avri.altman@....com,
        jejb@...ux.ibm.com, martin.petersen@...cle.com,
        asutoshd@...eaurora.org, stanley.chu@...iatek.com,
        bvanassche@....org, huobean@...il.com,
        ALIM AKHTAR <alim.akhtar@...sung.com>,
        linux-scsi@...r.kernel.org, linux-kernel@...r.kernel.org,
        JinHwan Park <jh.i.park@...sung.com>,
        Javier Gonzalez <javier.gonz@...sung.com>,
        SEUNGUK SHIN <seunguk.shin@...sung.com>,
        Sung-Jun Park <sungjun07.park@...sung.com>,
        Jinyoung CHOI <j-young.choi@...sung.com>,
        BoRam Shin <boram.shin@...sung.com>
Subject: Re: [PATCH v29 4/4] scsi: ufs: Add HPB 2.0 support

On 2021-03-15 09:31, Daejun Park wrote:
> This patch supports the HPB 2.0.
> 
> The HPB 2.0 supports read of varying sizes from 4KB to 512KB.
> In the case of Read (<= 32KB) is supported as single HPB read.
> In the case of Read (36KB ~ 512KB) is supported by as a combination of
> write buffer command and HPB read command to deliver more PPN.
> The write buffer commands may not be issued immediately due to busy 
> tags.
> To use HPB read more aggressively, the driver can requeue the write 
> buffer
> command. The requeue threshold is implemented as timeout and can be
> modified with requeue_timeout_ms entry in sysfs.
> 
> Signed-off-by: Daejun Park <daejun7.park@...sung.com>
> ---
> +static struct attribute *hpb_dev_param_attrs[] = {
> +	&dev_attr_requeue_timeout_ms.attr,
> +	NULL,
> +};
> +
> +struct attribute_group ufs_sysfs_hpb_param_group = {
> +	.name = "hpb_param_sysfs",
> +	.attrs = hpb_dev_param_attrs,
> +};
> +
> +static int ufshpb_pre_req_mempool_init(struct ufshpb_lu *hpb)
> +{
> +	struct ufshpb_req *pre_req = NULL;
> +	int qd = hpb->sdev_ufs_lu->queue_depth / 2;
> +	int i, j;
> +
> +	INIT_LIST_HEAD(&hpb->lh_pre_req_free);
> +
> +	hpb->pre_req = kcalloc(qd, sizeof(struct ufshpb_req), GFP_KERNEL);
> +	hpb->throttle_pre_req = qd;
> +	hpb->num_inflight_pre_req = 0;
> +
> +	if (!hpb->pre_req)
> +		goto release_mem;
> +
> +	for (i = 0; i < qd; i++) {
> +		pre_req = hpb->pre_req + i;
> +		INIT_LIST_HEAD(&pre_req->list_req);
> +		pre_req->req = NULL;
> +		pre_req->bio = NULL;

Why don't prepare bio as same as wb.m_page? Won't that save more time
for ufshpb_issue_pre_req()?

Thanks,
Can Guo.

> +
> +		pre_req->wb.m_page = alloc_page(GFP_KERNEL | __GFP_ZERO);
> +		if (!pre_req->wb.m_page) {
> +			for (j = 0; j < i; j++)
> +				__free_page(hpb->pre_req[j].wb.m_page);
> +
> +			goto release_mem;
> +		}
> +		list_add_tail(&pre_req->list_req, &hpb->lh_pre_req_free);
> +	}
> +
> +	return 0;
> +release_mem:
> +	kfree(hpb->pre_req);
> +	return -ENOMEM;
> +}
> +