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Tue, 31 Mar 2020 01:46:45 +0000 Received: from DGGEMS402-HUB.china.huawei.com (unknown [172.30.72.60]) by Forcepoint Email with ESMTP id 0A0148431BC035CFBB7C; Tue, 31 Mar 2020 09:46:36 +0800 (CST) Received: from [10.134.22.195] (10.134.22.195) by smtp.huawei.com (10.3.19.202) with Microsoft SMTP Server (TLS) id 14.3.487.0; Tue, 31 Mar 2020 09:46:31 +0800 To: Sahitya Tummala References: <1584506689-5041-1-git-send-email-stummala@codeaurora.org> <29d4adc4-482d-3d92-1470-3405989ea231@huawei.com> <20200326133700.GR20234@codeaurora.org> <2b0d8d4c-a981-4edc-d8ca-fe199a63ea79@huawei.com> <20200327030542.GS20234@codeaurora.org> <20200330065335.GT20234@codeaurora.org> <9adc5c7e-7936-bac7-58b1-50631f8ac5eb@huawei.com> <5ec3b2e1-162c-e62d-1834-100c8ae39ff7@huawei.com> <20200330105122.GV20234@codeaurora.org> From: Chao Yu Message-ID: Date: Tue, 31 Mar 2020 09:46:30 +0800 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: <20200330105122.GV20234@codeaurora.org> Content-Language: en-US X-Originating-IP: [10.134.22.195] X-CFilter-Loop: Reflected X-Headers-End: 1jJ5zH-00GB8N-8P Subject: Re: [f2fs-dev] [PATCH] f2fs: fix long latency due to discard during umount X-BeenThere: linux-f2fs-devel@lists.sourceforge.net X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Jaegeuk Kim , linux-kernel@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: linux-f2fs-devel-bounces@lists.sourceforge.net Hi Sahitya, On 2020/3/30 18:51, Sahitya Tummala wrote: > Hi Chao, > > On Mon, Mar 30, 2020 at 06:16:40PM +0800, Chao Yu wrote: >> 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; >> } >> > > Yes, I have also just figured out that as the reason. But most of the real block > devic drivers support MQ. Can we thus fix this case by checking for MQ status > before enabling REQ_NOWAIT as below? Please share your comments. > > diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c > index cda7935..e7e2ffe 100644 > --- a/fs/f2fs/segment.c > +++ b/fs/f2fs/segment.c > @@ -1131,7 +1131,9 @@ static int __submit_discard_cmd(struct f2fs_sb_info *sbi, > > flag = dpolicy->sync ? REQ_SYNC : 0; > - flag |= dpolicy->type == DPOLICY_UMOUNT ? REQ_NOWAIT : 0; > + > + if (sbi->sb->s_bdev->bd_queue && queue_is_mq(sbi->sb->s_bdev->bd_queue)) > + flag |= dpolicy->type == DPOLICY_UMOUNT ? REQ_NOWAIT : 0; IMO, it's too tight to couple with block layer logic? however, I don't have any better idea about the solution. Anyway, I guess we can Cc to Jan and block mailing list for comments to see whether there is a better solution. Thoughts? Thanks, > > if (dc->state != D_PREP) > return 0; > > Thanks, > >> >> >>> >>> 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 >>> . >>> > _______________________________________________ Linux-f2fs-devel mailing list Linux-f2fs-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel