From mboxrd@z Thu Jan 1 00:00:00 1970 From: Chao Yu Subject: Re: [PATCH] f2fs: enlarge block plug coverage Date: Tue, 10 Apr 2018 10:34:04 +0800 Message-ID: <967b8819-da9a-b609-6a22-db8df5c7ec6c@huawei.com> References: <20180404085404.82184-1-yuchao0@huawei.com> <20180405035115.GC50337@jaegeuk-macbookpro.roam.corp.google.com> <03c21c2f-cb0e-dbd4-b48a-95c2678964d1@huawei.com> <20180409180241.GC17558@jaegeuk-macbookpro.roam.corp.google.com> Mime-Version: 1.0 Content-Type: text/plain; charset="windows-1252" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20180409180241.GC17558@jaegeuk-macbookpro.roam.corp.google.com> Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org To: Jaegeuk Kim Cc: linux-f2fs-devel@lists.sourceforge.net, linux-kernel@vger.kernel.org, chao@kernel.org List-Id: linux-f2fs-devel.lists.sourceforge.net On 2018/4/10 2:02, Jaegeuk Kim wrote: > On 04/08, Chao Yu wrote: >> On 2018/4/5 11:51, Jaegeuk Kim wrote: >>> On 04/04, Chao Yu wrote: >>>> This patch enlarges block plug coverage in __issue_discard_cmd, in >>>> order to collect more pending bios before issuing them, to avoid >>>> being disturbed by previous discard I/O in IO aware discard mode. >>> >>> Hmm, then we need to wait for huge discard IO for over 10 secs, which >> >> We found that total discard latency is rely on total discard number we issued >> last time instead of range or length discard covered. IMO, if we don't change >> .max_requests value, we will not suffer longer latency. >> >>> will affect following read/write IOs accordingly. In order to avoid that, >>> we actually need to limit the discard size. Do you mean limit discard count or discard length? >> >> If you are worry about I/O interference in between discard and rw, I suggest to >> decrease .max_requests value. > > What do you mean? This will produce more pending requests in the queue? I mean after applying this patch, we can queue more discard IOs in plug inside task, otherwise, previous issued discard in block layer can make is_idle() be false, then it can stop IO awared user to issue pending discard command. Thanks, > >> >> Thanks, >> >>> >>> Thanks, >>> >>>> >>>> Signed-off-by: Chao Yu >>>> --- >>>> fs/f2fs/segment.c | 7 +++++-- >>>> 1 file changed, 5 insertions(+), 2 deletions(-) >>>> >>>> diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c >>>> index 8f0b5ba46315..4287e208c040 100644 >>>> --- a/fs/f2fs/segment.c >>>> +++ b/fs/f2fs/segment.c >>>> @@ -1208,10 +1208,12 @@ static int __issue_discard_cmd(struct f2fs_sb_info *sbi, >>>> pend_list = &dcc->pend_list[i]; >>>> >>>> mutex_lock(&dcc->cmd_lock); >>>> + >>>> + blk_start_plug(&plug); >>>> + >>>> if (list_empty(pend_list)) >>>> goto next; >>>> f2fs_bug_on(sbi, !__check_rb_tree_consistence(sbi, &dcc->root)); >>>> - blk_start_plug(&plug); >>>> list_for_each_entry_safe(dc, tmp, pend_list, list) { >>>> f2fs_bug_on(sbi, dc->state != D_PREP); >>>> >>>> @@ -1227,8 +1229,9 @@ static int __issue_discard_cmd(struct f2fs_sb_info *sbi, >>>> if (++iter >= dpolicy->max_requests) >>>> break; >>>> } >>>> - blk_finish_plug(&plug); >>>> next: >>>> + blk_finish_plug(&plug); >>>> + >>>> mutex_unlock(&dcc->cmd_lock); >>>> >>>> if (iter >= dpolicy->max_requests) >>>> -- >>>> 2.15.0.55.gc2ece9dc4de6 >>> >>> . >>> > > . >