On 07/24/2018 03:38 PM, Laura Abbott wrote:
> On 07/23/2018 09:24 PM, Mike Kravetz wrote:
>> With v4.17, I can see an issue like those addressed in commits 3c605096d315
>> ("mm/page_alloc: restrict max order of merging on isolated pageblock")
>> and d9dddbf55667 ("mm/page_alloc: prevent merging between isolated and
>> other pageblocks"). After running a CMA stress test for a while, I see:
>> MemTotal: 8168384 kB
>> MemFree: 8457232 kB
>> MemAvailable: 9204844 kB
>> If I let the test run, MemFree and MemAvailable will continue to grow.
>>
>> I am certain the issue is with pageblocks of migratetype ISOLATED. If
>> I disable all special 'is_migrate_isolate' checks in freepage accounting,
>> the issue goes away. Further, I am pretty sure the issue has to do with
>> pageblock merging and or page orders spanning pageblocks. If I make
>> pageblock_order equal MAX_ORDER-1, the issue also goes away.
>>
>> Just looking for suggesting in where/how to debug. I've been hacking on
>> this without much success.
>> --
>> Mike Kravetz
>>
>
> If you revert d883c6cf3b39 ("Revert "mm/cma: manage the memory of the CMA
> area by using the ZONE_MOVABLE"") do you still see the issue? I thought
> there was another isolation edge case which was fixed by that series.
>
Thanks Laura,
Reverting that patch certainly seems to help. Although, I'm guessing there
is still some accounting issue even with the patch reverted.
Right after boot,
MemTotal: 8168380 kB
MemFree: 7233360 kB
MemAvailable: 7317704 kB
After stress testing for a couple hours,
MemTotal: 8168380 kB
MemFree: 7848468 kB
MemAvailable: 7634856 kB
While looking at the code, I did not like the way set_migratetype_isolate
may 'isolate' more than pageblock_nr_pages if there is a > pageblock_order
sized free page. This seems to work because alloc_contig_range always
aligns to MAX_ORDER-1. But, I'd like to change this and see if it helps.
--
Mike Kravetz
