linux-kernel - Re: [PATCH v2 05/10] mm, hugetlb: fix and clean-up node iteration code to alloc or free

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Message-ID: <87r4eqm6gk.fsf@linux.vnet.ibm.com>
Date:	Tue, 23 Jul 2013 06:35:15 +0530
From:	"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>
To:	Michal Hocko <mhocko@...e.cz>, Joonsoo Kim <iamjoonsoo.kim@....com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Rik van Riel <riel@...hat.com>, Mel Gorman <mgorman@...e.de>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Hugh Dickins <hughd@...gle.com>,
	Davidlohr Bueso <davidlohr.bueso@...com>,
	David Gibson <david@...son.dropbear.id.au>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, Joonsoo Kim <js1304@...il.com>
Subject: Re: [PATCH v2 05/10] mm, hugetlb: fix and clean-up node iteration code to alloc or free

Michal Hocko <mhocko@...e.cz> writes:

> On Mon 22-07-13 17:36:26, Joonsoo Kim wrote:
>> Current node iteration code have a minor problem which do one more
>> node rotation if we can't succeed to allocate. For example,
>> if we start to allocate at node 0, we stop to iterate at node 0.
>> Then we start to allocate at node 1 for next allocation.
>> 
>> I introduce new macros "for_each_node_mask_to_[alloc|free]" and
>> fix and clean-up node iteration code to alloc or free.
>> This makes code more understandable.
>
> I don't know but it feels like you are trying to fix an awkward
> interface with another one. Why hstate_next_node_to_alloc cannot simply
> return MAX_NUMNODES once the loop is done and start from first_node next
> time it is called? We wouldn't have the bug you are mentioning and you
> do not need scary looking macros.
>

Even though the macros looks confusing, the changes do help rest of the
code. for ex: I liked how it made alloc simpler.

 +	for_each_node_mask_to_alloc(h, nr_nodes, node, nodes_allowed) {
 +		page = alloc_fresh_huge_page_node(h, node);

-aneesh

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