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

[Can Guo <cang@codeaurora.org>]

On 2021-03-18 10:02, Daejun Park wrote:
>> On 2021-03-17 09:42, Daejun Park wrote:
>>>> 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...
>>> 
>>> 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.
>> 
>> Can you elaborate please? Any error seen?
>> 
>> Per my understanding, in the case for pre_reqs, a bio is no different
>> from a page. Here it can reserve 16 pages for later use, which can be
>> done the same for bios.
> 
> I found some problem with re-using pre allocated bio.
> 
> The following kernel message is related with problem.
> [    2.750530] ------------[ cut here ]------------
> [    2.751404] WARNING: CPU: 4 PID: 170 at
> drivers/scsi/scsi_lib.c:1020 scsi_alloc_sgtables+0x253/0x2b0
> [    2.753054] Modules linked in:
> [    2.753651] CPU: 4 PID: 170 Comm: mount Not tainted 5.12.0-rc1+ #331
> [    2.754752] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996),
> BIOS rel-1.13.0-0-gf21b5a4aeb02-prebuilt.qemu.org 04/01/2014
> [    2.756813] RIP: 0010:scsi_alloc_sgtables+0x253/0x2b0
> [    2.757699] Code: 85 c0 74 19 41 0f b6 44 24 18 8d 50 e0 83 fa 03
> 76 30 41 bd 01 00 00 00 e9 1f fe ff ff be 01 00 00 00 45 31 ed e9 19
> fe ff ff <0f> 0b b8 0a f
> [    2.761021] RSP: 0018:ffffb06e0027f538 EFLAGS: 00010246
> [    2.761902] RAX: 0000000000000000 RBX: ffff9c3a42d424d0 RCX: 
> ffffb06e0027f5e0
> [    2.763184] RDX: ffff9c3a42d426a8 RSI: 0000000000000000 RDI: 
> ffff9c3a42d424d0
> [    2.764446] RBP: ffffb06e0027f570 R08: 0000000000000000 R09: 
> 0000000000000000
> [    2.765704] R10: ffffffff8eb0dda0 R11: 00000000fffb7675 R12: 
> ffff9c3a42d423c0
> [    2.766976] R13: 0000000000000000 R14: ffff9c3a41bed000 R15: 
> ffff9c3a420f4000
> [    2.768225] FS:  00007f42d1eab100(0000) GS:ffff9c3b77c00000(0000)
> knlGS:0000000000000000
> [    2.769666] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> [    2.770719] CR2: 00007f42d1ac1000 CR3: 0000000104bee006 CR4: 
> 0000000000370ee0
> [    2.771997] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 
> 0000000000000000
> [    2.773288] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 
> 0000000000000400
> [    2.774543] Call Trace:
> [    2.775092]  scsi_queue_rq+0x9b6/0xb20
> [    2.775754]  __blk_mq_try_issue_directly+0x150/0x1f0
> [    2.776636]  blk_mq_request_issue_directly+0x49/0x80
> [    2.777616]  blk_insert_cloned_request+0x85/0xd0
> [    2.778470]  ufshpb_prep.cold+0x793/0x7be
> [    2.779179]  ufshcd_queuecommand+0x114/0x690
> [    2.779986]  scsi_queue_rq+0x38a/0xb20
> [    2.780755]  blk_mq_dispatch_rq_list+0x13d/0x760
> [    2.781605]  ? dd_dispatch_request+0x67/0x1c0
> [    2.782337]  __blk_mq_do_dispatch_sched+0xb5/0x2c0
> [    2.783291]  __blk_mq_sched_dispatch_requests+0x13c/0x180
> [    2.784209]  blk_mq_sched_dispatch_requests+0x30/0x60
> [    2.785195]  __blk_mq_run_hw_queue+0x49/0x90
> [    2.786024]  __blk_mq_delay_run_hw_queue+0x162/0x180
> [    2.786890]  blk_mq_run_hw_queue+0x85/0xe0
> [    2.787590]  blk_mq_sched_insert_requests+0xdf/0x2b0
> [    2.788558]  blk_mq_flush_plug_list+0x118/0x240
> [    2.789405]  blk_flush_plug_list+0xde/0x110
> [    2.790225]  blk_finish_plug+0x21/0x30
> [    2.790878]  read_pages+0x16a/0x1d0
> [    2.791534]  page_cache_ra_unbounded+0x123/0x1c0
> [    2.792392]  do_page_cache_ra+0x38/0x40
> [    2.793183]  force_page_cache_ra+0x97/0x110
> [    2.793875]  page_cache_sync_ra+0x26/0x50
> [    2.794671]  filemap_get_pages+0xc8/0x4b0
> [    2.795482]  filemap_read+0xc9/0x340
> [    2.796144]  ? find_held_lock+0x31/0x90
> [    2.796809]  generic_file_read_iter+0xcc/0x130
> [    2.797644]  blkdev_read_iter+0x30/0x40
> [    2.798436]  new_sync_read+0x10e/0x190
> [    2.799112]  vfs_read+0x178/0x1d0
> [    2.799732]  ksys_read+0x6b/0xf0
> [    2.800361]  __x64_sys_read+0x15/0x20
> [    2.801027]  do_syscall_64+0x38/0x50
> [    2.801770]  entry_SYSCALL_64_after_hwframe+0x44/0xae
> [    2.802655] RIP: 0033:0x7f42d209a461
> [    2.803313] Code: fe ff ff 50 48 8d 3d fe d0 09 00 e8 e9 03 02 00
> 66 0f 1f 84 00 00 00 00 00 48 8d 05 99 62 0d 00 8b 00 85 c0 75 13 31
> c0 0f 05 <48> 3d 00 f0 8
> [    2.806632] RSP: 002b:00007ffe7b88bc88 EFLAGS: 00000246 ORIG_RAX:
> 0000000000000000
> [    2.807942] RAX: ffffffffffffffda RBX: 000055ccb2e070d0 RCX: 
> 00007f42d209a461
> [    2.809218] RDX: 0000000000040000 RSI: 00007f42d1ac1038 RDI: 
> 0000000000000004
> [    2.810482] RBP: 000055ccb2e07120 R08: 00007f42d1ac1010 R09: 
> 0000000000000000
> [    2.811729] R10: 0000000000000022 R11: 0000000000000246 R12: 
> 0000003b95fc0000
> [    2.813005] R13: 0000000000040000 R14: 00007f42d1ac1028 R15: 
> 00007f42d1ac1010
> [    2.814276] irq event stamp: 9319
> [    2.814868] hardirqs last  enabled at (9327): [<ffffffff8c4d2033>]
> console_unlock+0x4d3/0x5e0
> [    2.816349] hardirqs last disabled at (9336): [<ffffffff8c4d1fa6>]
> console_unlock+0x446/0x5e0
> [    2.817837] softirqs last  enabled at (8674): [<ffffffff8d4002ec>]
> __do_softirq+0x2ec/0x40f
> [    2.819298] softirqs last disabled at (8669): [<ffffffff8c46ad9e>]
> irq_exit_rcu+0xae/0xb0
> [    2.820744] ---[ end trace af3986a7787eeecf ]---
> 
> It is related to bi_iter value of bio is changed after use it.

Understood the problem now, let's take the 1st way -
1. prepare bios in ufshpb_pre_req_mempool_init() (leave 
bio_add_pc_page() where it was)
2. call bio_reset() in ufshpb_put_pre_req()

This should work.

Thanks,
Can Guo.

> 
> Thanks,
> Daejun
> 
>> This is not an enhancement, but a doubt - why not? Unless it is not
>> doable.
>> 
>> Thanks,
>> Can Guo.
>> 
>>> 
>>> 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;
>>>>>>>> +}
>>>>>>>> +
>>>>>>> 
>>>>>>> 
>>>>>>> 
>>>> 
>>>> 
>>>> 
>> 
>> 
>>