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SubjectRe: [PATCH 4/7] migrate_pages(): fix failure counting for THP subpages retrying
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On 6/27/2022 9:46 AM, Huang, Ying wrote:
> Baolin Wang <baolin.wang@linux.alibaba.com> writes:
>
>> On 6/24/2022 10:53 AM, Huang Ying wrote:
>>> If THP is failed to be migrated for -ENOSYS and -ENOMEM, the THP will
>>> be split into thp_split_pages, and after other pages are migrated,
>>> pages in thp_split_pages will be migrated with no_subpage_counting ==
>>> true, because its failure have been counted already. If some pages in
>>> thp_split_pages are retried during migration, we should not count
>>> their failure if no_subpage_counting == true too. This is done this
>>> patch to fix the failure counting for THP subpages retrying.
>>
>> Good catch. Totally agree with you. It seems we can move the condition
>> into -EAGAIN case like other cases did?
>>
>> diff --git a/mm/migrate.c b/mm/migrate.c
>> index 1ece23d80bc4..491c2d07402b 100644
>> --- a/mm/migrate.c
>> +++ b/mm/migrate.c
>> @@ -1463,7 +1463,7 @@ int migrate_pages(struct list_head *from,
>> new_page_t get_new_page,
>> case -EAGAIN:
>> if (is_thp)
>> thp_retry++;
>> - else
>> + else if (!no_subpage_counting)
>> retry++;
>> break;
>
> This has another effect except fixing the failure counting. That is,
> the split subpages of THP will not be retried for 10 times for -EAGAIN.

Ah, yes.

> TBH, I think that we should do that. But because this has some behavior

OK. So you afraid that 10 times retry for each subpage of THP will waste
lots of time?

> change, it's better to be done in a separate patch? Do you have
> interest to do that on top of this patchset?

Sure. I can send a patch which can be folded into your series. Is this
OK for you?

By the way, if I do like I said, the patch 4 can be avoided.

>
>> Anyway this patch looks good to me.
>> Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>
>
> Thanks!
>
> Best Regards,
> Huang, Ying
>
>>> Signed-off-by: "Huang, Ying" <ying.huang@intel.com>
>>> Fixes: 5984fabb6e82 ("mm: move_pages: report the number of non-attempted pages")
>>> Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
>>> Cc: Zi Yan <ziy@nvidia.com>
>>> Cc: Yang Shi <shy828301@gmail.com>
>>> --- > mm/migrate.c | 3 ++-
>>> 1 file changed, 2 insertions(+), 1 deletion(-)
>>> diff --git a/mm/migrate.c b/mm/migrate.c
>>> index 542533e4e3cf..61dab3025a1d 100644
>>> --- a/mm/migrate.c
>>> +++ b/mm/migrate.c
>>> @@ -1477,7 +1477,8 @@ int migrate_pages(struct list_head *from, new_page_t get_new_page,
>>> }
>>> }
>>> }
>>> - nr_failed += retry;
>>> + if (!no_subpage_counting)
>>> + nr_failed += retry;
>>> nr_thp_failed += thp_retry;
>>> /*
>>> * Try to migrate subpages of fail-to-migrate THPs, no nr_failed

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