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 <yuch...@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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