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Date: Mon, 18 Jul 2016 10:05:44 +0200 From: Vlastimil Babka <vbabka@...e.cz> To: Xishi Qiu <qiuxishi@...wei.com>, Joonsoo Kim <iamjoonsoo.kim@....com> Cc: David Rientjes <rientjes@...gle.com>, Andrew Morton <akpm@...ux-foundation.org>, Naoya Horiguchi <n-horiguchi@...jp.nec.com>, Linux MM <linux-mm@...ck.org>, LKML <linux-kernel@...r.kernel.org> Subject: Re: [PATCH 1/2] mem-hotplug: use GFP_HIGHUSER_MOVABLE in, alloc_migrate_target() On 07/18/2016 10:00 AM, Xishi Qiu wrote: > On 2016/7/18 13:51, Joonsoo Kim wrote: > >> On Fri, Jul 15, 2016 at 10:47:06AM +0800, Xishi Qiu wrote: >>> alloc_migrate_target() is called from migrate_pages(), and the page >>> is always from user space, so we can add __GFP_HIGHMEM directly. >> >> No, all migratable pages are not from user space. For example, >> blockdev file cache has __GFP_MOVABLE and migratable but it has no >> __GFP_HIGHMEM and __GFP_USER. >> > > Hi Joonsoo, > > So the original code "gfp_t gfp_mask = GFP_USER | __GFP_MOVABLE;" > is not correct? It's not incorrect. GFP_USER just specifies some reclaim flags, and may perhaps restrict allocation through __GFP_HARDWALL, where the original page could have been allocated without the restriction. But it doesn't put the place in an unexpected address range, as placing a non-highmem page into highmem could. __GFP_MOVABLE then just controls a heuristic for placement within a zone. >> And, zram's memory isn't GFP_HIGHUSER_MOVABLE but has __GFP_MOVABLE. >> > > Can we distinguish __GFP_MOVABLE or GFP_HIGHUSER_MOVABLE when doing > mem-hotplug? I don't understand the question here, can you rephrase with more detail? Thanks. > Thanks, > Xishi Qiu > >> Thanks. >> >> >> . >> > > >
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