Re: [RFC PATCH 2/3] mm, compaction: use MIN_COMPACT_COSTLY_PRIORITY everywhere for costly orders

[Vlastimil Babka]

On 8/1/19 10:33 PM, Mike Kravetz wrote:
> On 8/1/19 6:01 AM, Vlastimil Babka wrote:
>> Could you try testing the patch below instead? It should hopefully
>> eliminate the stalls. If it makes hugepage allocation give up too early,
>> we'll know we have to involve __GFP_RETRY_MAYFAIL in allowing the
>> MIN_COMPACT_PRIORITY priority. Thanks!
> 
> Thanks.  This patch does eliminate the stalls I was seeing.

Great, thanks! I'll send a proper patch then.

> In my testing, there is little difference in how many hugetlb pages are
> allocated.  It does not appear to be giving up/failing too early.  But,
> this is only with __GFP_RETRY_MAYFAIL.  The real concern would with THP
> requests.  Any suggestions on how to test that?

AFAICS the default THP defrag mode is unaffected, as GFP_TRANSHUGE_LIGHT doesn't
include __GFP_DIRECT_RECLAIM, so it never reaches this code. Madvised THP
allocations will be affected, which should best be tested the same way as Andrea
and Mel did in the __GFP_THISNODE debate.