linux-kernel - Re: [PATCH RFC 1/2] mm, hugetlb: unify core page allocation accounting and initialization

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Date:   Wed, 29 Nov 2017 11:09:26 -0800
From:   Mike Kravetz <mike.kravetz@...cle.com>
To:     Michal Hocko <mhocko@...nel.org>
Cc:     linux-mm@...ck.org, Naoya Horiguchi <n-horiguchi@...jp.nec.com>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH RFC 1/2] mm, hugetlb: unify core page allocation
 accounting and initialization

On 11/28/2017 10:57 PM, Michal Hocko wrote:
> On Tue 28-11-17 13:34:53, Mike Kravetz wrote:
>> On 11/28/2017 06:12 AM, Michal Hocko wrote:
> [...]
>>> +/*
>>> + * Allocates a fresh page to the hugetlb allocator pool in the node interleaved
>>> + * manner.
>>> + */
>>>  static int alloc_fresh_huge_page(struct hstate *h, nodemask_t *nodes_allowed)
>>>  {
>>>  	struct page *page;
>>>  	int nr_nodes, node;
>>> -	int ret = 0;
>>> +	gfp_t gfp_mask = htlb_alloc_mask(h) | __GFP_THISNODE;
>>>  
>>>  	for_each_node_mask_to_alloc(h, nr_nodes, node, nodes_allowed) {
>>> -		page = alloc_fresh_huge_page_node(h, node);
>>> -		if (page) {
>>> -			ret = 1;
>>> +		page = __hugetlb_alloc_buddy_huge_page(h, gfp_mask,
>>> +				node, nodes_allowed);
>>
>> I don't have the greatest understanding of node/nodemasks, but ...
>> Since __hugetlb_alloc_buddy_huge_page calls __alloc_pages_nodemask(), do
>> we still need to explicitly iterate over nodes with
>> for_each_node_mask_to_alloc() here?
> 
> Yes we do, because callers depend on the round robin allocation policy
> which is implemented by the ugly for_each_node_mask_to_alloc. I am not
> saying I like the way this is done but this is user visible thing.

Ah, thanks.

I missed the __GFP_THISNODE.  Because of that, the nodes_allowed mask is
not used in the allocation attempts.  So, cycling through the nodes with
the for_each_node_mask_to_alloc makes sense.

> Or maybe I've missunderstood the whole thing...

No, this should preserve the original behavior.

-- 
Mike Kravetz