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Date: Thu, 22 May 2014 10:43:07 +0200 From: Vlastimil Babka <vbabka@...e.cz> To: David Rientjes <rientjes@...gle.com> CC: Andrew Morton <akpm@...ux-foundation.org>, Mel Gorman <mgorman@...e.de>, Rik van Riel <riel@...hat.com>, Joonsoo Kim <iamjoonsoo.kim@....com>, Greg Thelen <gthelen@...gle.com>, Hugh Dickins <hughd@...gle.com>, linux-kernel@...r.kernel.org, linux-mm@...ck.org Subject: Re: [patch -mm] mm, thp: avoid excessive compaction latency during fault fix 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. > -- > To unsubscribe, send a message with 'unsubscribe linux-mm' in > the body to majordomo@...ck.org. For more info on Linux MM, > see: http://www.linux-mm.org/ . > Don't email: <a href=mailto:"dont@...ck.org"> email@...ck.org </a> > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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