Messages in this thread Patch in this message | | | Subject | Re: [f2fs-dev] [PATCH] f2fs: fix long latency due to discard during umount | From | Chao Yu <> | Date | Mon, 30 Mar 2020 18:16:40 +0800 |
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On 2020/3/30 16:38, Chao Yu wrote: > 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
I use zram as backend device of fstest,
Call Trace: dump_stack+0x66/0x8b f2fs_submit_discard_endio+0x88/0xa0 [f2fs] generic_make_request_checks+0x70/0x5f0 generic_make_request+0x3e/0x2e0 submit_bio+0x72/0x140 __submit_discard_cmd.isra.50+0x4a8/0x710 [f2fs] __issue_discard_cmd+0x171/0x3a0 [f2fs]
Does this mean zram uses single queue, so we may always fail to submit 'nowait' IO due to below condition:
/* * Non-mq queues do not honor REQ_NOWAIT, so complete a bio * with BLK_STS_AGAIN status in order to catch -EAGAIN and * to give a chance to the caller to repeat request gracefully. */ if ((bio->bi_opf & REQ_NOWAIT) && !queue_is_mq(q)) { status = BLK_STS_AGAIN; goto end_io; }
> > 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. >> > > > _______________________________________________ > Linux-f2fs-devel mailing list > Linux-f2fs-devel@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel > . >
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