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Date: Mon, 30 Mar 2020 16:38:11 +0800
From: Chao Yu <yuchao0@...wei.com>
To: Sahitya Tummala <stummala@...eaurora.org>
CC: Jaegeuk Kim <jaegeuk@...nel.org>,
<linux-f2fs-devel@...ts.sourceforge.net>,
<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] f2fs: fix long latency due to discard during umount
Hi Sahitya,
Bad news, :( I guess we didn't catch the root cause, as after applying v3,
I still can reproduce this issue:
generic/003 10s ... 30s
Thanks,
On 2020/3/30 14:53, Sahitya Tummala wrote:
> Hi Chao,
>
> On Fri, Mar 27, 2020 at 08:35:42AM +0530, Sahitya Tummala wrote:
>> On Fri, Mar 27, 2020 at 09:51:43AM +0800, Chao Yu wrote:
>>>
>>> With this patch, most of xfstest cases cost 5 * n second longer than before.
>>>
>>> E.g. generic/003, during umount(), we looped into retrying one bio
>>> submission.
>>>
>>> [61279.829724] F2FS-fs (zram1): Found nat_bits in checkpoint
>>> [61279.885337] F2FS-fs (zram1): Mounted with checkpoint version = 5cf3cb8e
>>> [61281.912832] submit discard bio start [23555,1]
>>> [61281.912835] f2fs_submit_discard_endio [23555,1] err:-11
>>> [61281.912836] submit discard bio end [23555,1]
>>> [61281.912836] move dc to retry list [23555,1]
>>>
>>> ...
>>>
>>> [61286.881212] submit discard bio start [23555,1]
>>> [61286.881217] f2fs_submit_discard_endio [23555,1] err:-11
>>> [61286.881223] submit discard bio end [23555,1]
>>> [61286.881224] move dc to retry list [23555,1]
>>> [61286.905198] submit discard bio start [23555,1]
>>> [61286.905203] f2fs_submit_discard_endio [23555,1] err:-11
>>> [61286.905205] submit discard bio end [23555,1]
>>> [61286.905206] move dc to retry list [23555,1]
>>> [61286.929157] F2FS-fs (zram1): Issue discard(23555, 23555, 1) failed, ret: -11
>>>
>>> Could you take a look at this issue?
>>
>> Let me check and get back on this.
>
> I found the issue. The dc with multiple bios is getting requeued again and
> again in case if one of its bio gets -EAGAIN error. Even the successfully
> completed bios are getting requeued again resulting into long latency.
> I have fixed it by splitting the dc in such case so that we can requeue only
> the leftover bios into a new dc and retry that later within the 5 sec timeout.
>
> Please help to review v3 posted and if it looks good, I would like to request
> you to test the earlier regression scenario with it to check the result again?
>
> thanks,
>
>>
>> Thanks,
>>
>>>
>>> Thanks,
>>>
>>>>
>>>> Thanks,
>>>>
>>>>> Thanks,
>>>>>
>>>>>> + break;
>>>>>> + }
>>>>>> + }
>>>>>>
>>>>>> atomic_inc(&dcc->issued_discard);
>>>>>>
>>>>>> @@ -1463,6 +1477,40 @@ static unsigned int __issue_discard_cmd_orderly(struct f2fs_sb_info *sbi,
>>>>>> return issued;
>>>>>> }
>>>>>>
>>>>>> +static bool __should_discard_retry(struct f2fs_sb_info *sbi,
>>>> s> > + struct discard_policy *dpolicy)
>>>>>> +{
>>>>>> + struct discard_cmd_control *dcc = SM_I(sbi)->dcc_info;
>>>>>> + struct discard_cmd *dc, *tmp;
>>>>>> + bool retry = false;
>>>>>> + unsigned long flags;
>>>>>> +
>>>>>> + if (dpolicy->type != DPOLICY_UMOUNT)
>>>>>> + f2fs_bug_on(sbi, 1);
>>>>>> +
>>>>>> + mutex_lock(&dcc->cmd_lock);
>>>>>> + list_for_each_entry_safe(dc, tmp, &(dcc->retry_list), list) {
>>>>>> + if (dpolicy->timeout != 0 &&
>>>>>> + f2fs_time_over(sbi, dpolicy->timeout)) {
>>>>>> + retry = false;
>>>>>> + break;
>>>>>> + }
>>>>>> +
>>>>>> + spin_lock_irqsave(&dc->lock, flags);
>>>>>> + if (!dc->bio_ref) {
>>>>>> + dc->state = D_PREP;
>>>>>> + dc->error = 0;
>>>>>> + reinit_completion(&dc->wait);
>>>>>> + __relocate_discard_cmd(dcc, dc);
>>>>>> + retry = true;
>>>>>> + }
>>>>>> + spin_unlock_irqrestore(&dc->lock, flags);
>>>>>> + }
>>>>>> + mutex_unlock(&dcc->cmd_lock);
>>>>>> +
>>>>>> + return retry;
>>>>>> +}
>>>>>> +
>>>>>> static int __issue_discard_cmd(struct f2fs_sb_info *sbi,
>>>>>> struct discard_policy *dpolicy)
>>>>>> {
>>>>>> @@ -1470,12 +1518,13 @@ static int __issue_discard_cmd(struct f2fs_sb_info *sbi,
>>>>>> struct list_head *pend_list;
>>>>>> struct discard_cmd *dc, *tmp;
>>>>>> struct blk_plug plug;
>>>>>> - int i, issued = 0;
>>>>>> + int i, err, issued = 0;
>>>>>> bool io_interrupted = false;
>>>>>>
>>>>>> if (dpolicy->timeout != 0)
>>>>>> f2fs_update_time(sbi, dpolicy->timeout);
>>>>>>
>>>>>> +retry:
>>>>>> for (i = MAX_PLIST_NUM - 1; i >= 0; i--) {
>>>>>> if (dpolicy->timeout != 0 &&
>>>>>> f2fs_time_over(sbi, dpolicy->timeout))
>>>>>> @@ -1509,7 +1558,10 @@ static int __issue_discard_cmd(struct f2fs_sb_info *sbi,
>>>>>> break;
>>>>>> }
>>>>>>
>>>>>> - __submit_discard_cmd(sbi, dpolicy, dc, &issued);
>>>>>> + err = __submit_discard_cmd(sbi, dpolicy, dc, &issued);
>>>>>> + if (err == -EAGAIN)
>>>>>> + congestion_wait(BLK_RW_ASYNC,
>>>>>> + DEFAULT_IO_TIMEOUT);
>>>>>>
>>>>>> if (issued >= dpolicy->max_requests)
>>>>>> break;
>>>>>> @@ -1522,6 +1574,10 @@ static int __issue_discard_cmd(struct f2fs_sb_info *sbi,
>>>>>> break;
>>>>>> }
>>>>>>
>>>>>> + if (!list_empty(&dcc->retry_list) &&
>>>>>> + __should_discard_retry(sbi, dpolicy))
>>>>>> + goto retry;
>>>>>> +
>>>>>> if (!issued && io_interrupted)
>>>>>> issued = -1;
>>>>>>
>>>>>> @@ -1613,6 +1669,12 @@ static unsigned int __wait_discard_cmd_range(struct f2fs_sb_info *sbi,
>>>>>> goto next;
>>>>>> }
>>>>>>
>>>>>> + if (dpolicy->type == DPOLICY_UMOUNT &&
>>>>>> + !list_empty(&dcc->retry_list)) {
>>>>>> + wait_list = &dcc->retry_list;
>>>>>> + goto next;
>>>>>> + }
>>>>>> +
>>>>>> return trimmed;
>>>>>> }
>>>>>>
>>>>>> @@ -2051,6 +2113,7 @@ static int create_discard_cmd_control(struct f2fs_sb_info *sbi)
>>>>>> for (i = 0; i < MAX_PLIST_NUM; i++)
>>>>>> INIT_LIST_HEAD(&dcc->pend_list[i]);
>>>>>> INIT_LIST_HEAD(&dcc->wait_list);
>>>>>> + INIT_LIST_HEAD(&dcc->retry_list);
>>>>>> INIT_LIST_HEAD(&dcc->fstrim_list);
>>>>>> mutex_init(&dcc->cmd_lock);
>>>>>> atomic_set(&dcc->issued_discard, 0);
>>>>>>
>>>>
>>
>> --
>> --
>> Sent by a consultant of the Qualcomm Innovation Center, Inc.
>> The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum.
>
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