Messages in this thread | | | Date | Thu, 22 May 2014 10:43:07 +0200 | From | Vlastimil Babka <> | Subject | Re: [patch -mm] mm, thp: avoid excessive compaction latency during fault fix |
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On 05/22/2014 04:49 AM, David Rientjes wrote: > On Tue, 13 May 2014, Vlastimil Babka wrote: > >> I wonder what about a process doing e.g. mmap() with MAP_POPULATE. It seems to >> me that it would get only MIGRATE_ASYNC here, right? Since gfp_mask would >> include __GFP_NO_KSWAPD and it won't have PF_KTHREAD. >> I think that goes against the idea that with MAP_POPULATE you say you are >> willing to wait to have everything in place before you actually use the >> memory. So I guess you are also willing to wait for hugepages in that >> situation? >> > > I don't understand the distinction you're making between MAP_POPULATE and > simply a prefault of the anon memory. What is the difference in semantics > between using MAP_POPULATE and touching a byte every page size along the > range? In the latter, you'd be faulting thp with MIGRATE_ASYNC, so I > don't understand how MAP_POPULATE is any different or implies any > preference for hugepages.
Hm, OK. It's right we cannot distinguish populating by touching the pages manually. Nevermind then.
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