linux-kernel - Re: [PATCH 3/3] mm/mmap.c: extract __vma_unlink_list as counter part for __vma_link

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Date:   Wed, 21 Aug 2019 09:22:44 +0800
From:   Wei Yang <richardw.yang@...ux.intel.com>
To:     Matthew Wilcox <willy@...radead.org>
Cc:     Wei Yang <richardw.yang@...ux.intel.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Christoph Hellwig <hch@...radead.org>,
        akpm@...ux-foundation.org, mgorman@...hsingularity.net,
        osalvador@...e.de, linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/3] mm/mmap.c: extract __vma_unlink_list as counter part
 for __vma_link_list

On Tue, Aug 20, 2019 at 05:54:17PM -0700, Matthew Wilcox wrote:
>On Wed, Aug 21, 2019 at 08:52:34AM +0800, Wei Yang wrote:
>> On Tue, Aug 20, 2019 at 10:26:29AM -0700, Matthew Wilcox wrote:
>> >On Wed, Aug 14, 2019 at 11:19:37AM +0200, Vlastimil Babka wrote:
>> >> On 8/14/19 8:57 AM, Wei Yang wrote:
>> >> > On Tue, Aug 13, 2019 at 10:16:11PM -0700, Christoph Hellwig wrote:
>> >> >>Btw, is there any good reason we don't use a list_head for vma linkage?
>> >> > 
>> >> > Not sure, maybe there is some historical reason?
>> >> 
>> >> Seems it was single-linked until 2010 commit 297c5eee3724 ("mm: make the vma
>> >> list be doubly linked") and I guess it was just simpler to add the vm_prev link.
>> >> 
>> >> Conversion to list_head might be an interesting project for some "advanced
>> >> beginner" in the kernel :)
>> >
>> >I'm working to get rid of vm_prev and vm_next, so it would probably be
>> >wasted effort.
>> 
>> You mean replace it with list_head?
>
>No, replace the rbtree with a new tree.  https://lwn.net/Articles/787629/

Sounds interesting.

While I am not sure the plan is settled down, and how long it would take to
replace the rb_tree with maple tree. I guess it would probably take some time
to get merged upstream.

IMHO, it would be good to have this cleanup in current kernel. Do you agree?

-- 
Wei Yang
Help you, Help me