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

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Date:   Wed, 17 Mar 2021 10:42:53 +0900
From:   Daejun Park <daejun7.park@...sung.com>
To:     Can Guo <cang@...eaurora.org>,
        Daejun Park <daejun7.park@...sung.com>
CC:     Greg KH <gregkh@...uxfoundation.org>,
        "avri.altman@....com" <avri.altman@....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>,
        "bvanassche@....org" <bvanassche@....org>,
        "huobean@...il.com" <huobean@...il.com>,
        ALIM AKHTAR <alim.akhtar@...sung.com>,
        "linux-scsi@...r.kernel.org" <linux-scsi@...r.kernel.org>,
        "linux-kernel@...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: Re: [PATCH v29 4/4] scsi: ufs: Add HPB 2.0 support

>On 2021-03-15 15:23, Can Guo wrote:
>> On 2021-03-15 15:07, 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()?
>>> 
>>> It is pre_req pool. So although we prepare bio at this time, it just
>>> only for first pre_req.
>> 
>> I meant removing the bio_alloc() in ufshpb_issue_pre_req() and 
>> bio_put()
>> in ufshpb_pre_req_compl_fn(). bios, in pre_req's case, just hold a 
>> page.
>> So, prepare 16 (if queue depth is 32) bios here, just use them along 
>> with
>> wb.m_page and call bio_reset() in ufshpb_pre_req_compl_fn(). Shall it 
>> work?
>> 
> 
>If it works, you can even have the bio_add_pc_page() called here. Later 
>in
>ufshpb_execute_pre_req(), you don't need to call 
>ufshpb_pre_req_add_bio_page(),
>just call ufshpb_prep_entry() once instead - it save many repeated steps 
>for a
>pre_req, and you don't even need to call bio_reset() in this case, since 
>for a
>bio, nothing changes after it is binded with a specific page...

Hi, Can Guo

I tried the idea that you suggested, but it doesn't work properly.
This optimization should be done next time for enhancement.

Thanks
Daejun

>Can Guo.
> 
>> Thanks,
>> Can Guo.
>> 
>>> After use it, it should be prepared bio at issue phase.
>>> 
>>> Thanks,
>>> Daejun
>>> 
>>>> 
>>>> 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;
>>>>> +}
>>>>> +
>>>> 
>>>> 
>>>> 
> 
> 
>