linux-kernel - Re: [RFC v2 1/4] mm: make alloc_pages_exact_node pass __GFP

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Date:	Mon, 27 Jul 2015 17:47:44 +0200
From:	Vlastimil Babka <vbabka@...e.cz>
To:	Johannes Weiner <hannes@...xchg.org>
Cc:	linux-mm@...ck.org, linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	Mel Gorman <mgorman@...e.de>,
	David Rientjes <rientjes@...gle.com>,
	Greg Thelen <gthelen@...gle.com>,
	"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>,
	Christoph Lameter <cl@...ux.com>,
	Pekka Enberg <penberg@...nel.org>,
	Joonsoo Kim <iamjoonsoo.kim@....com>,
	Naoya Horiguchi <n-horiguchi@...jp.nec.com>
Subject: Re: [RFC v2 1/4] mm: make alloc_pages_exact_node pass __GFP_THISNODE

On 07/27/2015 05:39 PM, Johannes Weiner wrote:
> On Fri, Jul 24, 2015 at 04:45:23PM +0200, Vlastimil Babka wrote:
>> @@ -310,11 +326,18 @@ static inline struct page *alloc_pages_node(int nid, gfp_t gfp_mask,
>>   	return __alloc_pages(gfp_mask, order, node_zonelist(nid, gfp_mask));
>>   }
>>
>> +/*
>> + * Allocate pages, restricting the allocation to the node given as nid. The
>> + * node must be valid and online. This is achieved by adding __GFP_THISNODE
>> + * to gfp_mask.
>> + */
>>   static inline struct page *alloc_pages_exact_node(int nid, gfp_t gfp_mask,
>>   						unsigned int order)
>>   {
>>   	VM_BUG_ON(nid < 0 || nid >= MAX_NUMNODES || !node_online(nid));
>>
>> +	gfp_mask |= __GFP_THISNODE;
>> +
>>   	return __alloc_pages(gfp_mask, order, node_zonelist(nid, gfp_mask));
>>   }
>
> The "exact" name is currently ambiguous within the allocator API, and
> it's bad that we have _exact_node() and _exact_nid() with entirely
> different meanings. It'd be good to make "thisnode" refer to specific
> and exclusive node requests, and "exact" to mean page allocation
> chunks that are not in powers of two.

Ugh, good point.

> Would you consider renaming this function to alloc_pages_thisnode() as
> part of this series?

Sure, let's do it properly while at it. Yet "thisnode" is somewhat 
misleading name as it might imply the cpu's local node. The same applies 
to __GFP_THISNODE. So maybe find a better name for both? restrict_node? 
single_node?

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