Messages in this thread |  | | Subject | Re: [PATCH] f2fs: enlarge block plug coverage | From | Chao Yu <> | Date | Tue, 10 Apr 2018 10:34:04 +0800 |
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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 <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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