Messages in this thread | | | Date | Thu, 12 Apr 2018 18:06:15 -0700 | From | Jaegeuk Kim <> | Subject | Re: [PATCH] f2fs: enlarge block plug coverage |
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On 04/10, Chao Yu wrote: > On 2018/4/10 12:10, Jaegeuk Kim wrote: > > On 04/10, Chao Yu wrote: > >> 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? > > > > Both of them. > > > >> > >>>> > >>>> 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. > > > > Then, unplug will issue lots of discard commands, which affects the following rw > > latencies. My preference would be issuing discard commands one by one as much as > > possible. > > Hmm.. for you concern, we can turn down IO priority of discard from background?
That makes much more sense to me. :P
> > Thanks, > > > > >> > >> Thanks, > >> > >>> > >>>> > >>>> Thanks, > >>>> > >>>>> > >>>>> Thanks, > >>>>> > >>>>>> > >>>>>> Signed-off-by: Chao Yu <yuchao0@huawei.com> > >>>>>> --- > >>>>>> 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 > >>>>> > >>>>> . > >>>>> > >>> > >>> . > >>> > > > > . > >
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