Messages in this thread | | | Date | Thu, 12 Apr 2018 21:07:02 -0700 | From | Jaegeuk Kim <> | Subject | Re: [PATCH] f2fs: enlarge block plug coverage |
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On 04/13, Chao Yu wrote: > On 2018/4/13 9:06, Jaegeuk Kim wrote: > > 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 > > Then, this patch which enlarge plug coverage will not still a problem, right? ;)
This is different one.
> > Thanks, > > > > >> > >> 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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