linux-kernel - Re: [PATCH 1/2] mem-hotplug: use GFP_HIGHUSER_MOVABLE in, alloc_migrate

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Date:	Mon, 18 Jul 2016 16:00:10 +0800
From:	Xishi Qiu <qiuxishi@...wei.com>
To:	Joonsoo Kim <iamjoonsoo.kim@....com>
CC:	David Rientjes <rientjes@...gle.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Vlastimil Babka <vbabka@...e.cz>,
	"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 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?

> 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?

Thanks,
Xishi Qiu

> Thanks.
> 
> 
> .
>