linux-kernel - Re: [LSF/MM TOPIC] Using XArray to manage the VMA

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Date:   Fri, 29 Mar 2019 10:31:45 +0100
From:   Laurent Dufour <ldufour@...ux.ibm.com>
To:     Matthew Wilcox <willy@...radead.org>,
        Michel Lespinasse <walken@...gle.com>,
        David Rientjes <rientjes@...gle.com>
Cc:     lsf-pc@...ts.linux-foundation.org, Linux-MM <linux-mm@...ck.org>,
        linux-kernel@...r.kernel.org,
        "Liam R. Howlett" <Liam.Howlett@...cle.com>
Subject: Re: [LSF/MM TOPIC] Using XArray to manage the VMA

Adding Michel and David in the loop who are interested in this topic too.

Le 13/03/2019 à 19:01, Matthew Wilcox a écrit :
> On Wed, Mar 13, 2019 at 04:10:14PM +0100, Laurent Dufour wrote:
>> If this is not too late and if there is still place available, I would like
>> to attend the MM track and propose a topic about using the XArray to replace
>> the VMA's RB tree and list.
> 
> If there isn't room on the schedule, then Laurent and I are definitely
> going to sneak off and talk about this ourselves at some point.  Having a
> high-bandwidth conversation about this is going to be really important
> for us, and I think having other people involved would be good.
> 
> If there're still spots, it'd be good to have Liam Howlett join us.
> He's doing the actual writing-of-code for the Maple Tree at the moment
> (I did some earlier on, but recent commits are all him).
> 
>> Using the XArray in place of the VMA's tree and list seems to be a first
>> step to the long way of removing/replacing the mmap_sem.
>> However, there are still corner cases to address like the VMA splitting and
>> merging which may raise some issue. Using the XArray's specifying locking
>> would not be enough to handle the memory management, and additional fine
>> grain locking like a per VMA one could be studied, leading to further
>> discussion about the merging of the VMA.
>>
>> In addition, here are some topics I'm interested in:
>> - Test cases to choose for demonstrating mm features or fixing mm bugs
>> proposed by Balbir Singh
>> - mm documentation proposed by Mike Rapoport
>>
>> Laurent.
>>
>