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SubjectRe: [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@samsung.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...

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;
>>>> +}
>>>> +
>>>
>>>
>>>

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