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

[Daejun Park]

>> 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@xxxxxxxxxxx>
>> ---
>> +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.
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;
>> +}
>> +
> 
> 
>