Re: [PATCH] mm/compaction: count pages and stop correctly during page isolation.

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



On 30 Oct 2020, at 5:43, Michal Hocko wrote:

> [Cc Vlastimil]
>
> On Thu 29-10-20 16:04:35, Zi Yan wrote:
>> From: Zi Yan <ziy@xxxxxxxxxx>
>>
>> In isolate_migratepages_block, when cc->alloc_contig is true, we are
>> able to isolate compound pages, nr_migratepages and nr_isolated did not
>> count compound pages correctly, causing us to isolate more pages than we
>> thought. Use thp_nr_pages to count pages. Otherwise, we might be trapped
>> in too_many_isolated while loop, since the actual isolated pages can go
>> up to COMPACT_CLUSTER_MAX*512=16384, where COMPACT_CLUSTER_MAX is 32,
>> since we stop isolation after cc->nr_migratepages reaches to
>> COMPACT_CLUSTER_MAX.
>>
>> In addition, after we fix the issue above, cc->nr_migratepages could
>> never be equal to COMPACT_CLUSTER_MAX if compound pages are isolated,
>> thus page isolation could not stop as we intended. Change the isolation
>> stop condition to >=.
>>
>> Signed-off-by: Zi Yan <ziy@xxxxxxxxxx>
>> ---
>>  mm/compaction.c | 8 ++++----
>>  1 file changed, 4 insertions(+), 4 deletions(-)
>>
>> diff --git a/mm/compaction.c b/mm/compaction.c
>> index ee1f8439369e..0683a4999581 100644
>> --- a/mm/compaction.c
>> +++ b/mm/compaction.c
>> @@ -1012,8 +1012,8 @@ isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn,
>>
>>  isolate_success:
>>  		list_add(&page->lru, &cc->migratepages);
>> -		cc->nr_migratepages++;
>> -		nr_isolated++;
>> +		cc->nr_migratepages += thp_nr_pages(page);
>> +		nr_isolated += thp_nr_pages(page);
>
> Does thp_nr_pages work for __PageMovable pages?

Yes. It is the same as compound_nr() but compiled
to 1 when THP is not enabled.

—
Best Regards,
Yan Zi

Attachment: signature.asc
Description: OpenPGP digital signature


[Index of Archives]     [Linux ARM Kernel]     [Linux ARM]     [Linux Omap]     [Fedora ARM]     [IETF Annouce]     [Bugtraq]     [Linux OMAP]     [Linux MIPS]     [eCos]     [Asterisk Internet PBX]     [Linux API]

  Powered by Linux