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From: Davidlohr Bueso <dave@stgolabs.net>
To: Matthew Wilcox <willy@infradead.org>
Cc: Laurent Dufour <ldufour@linux.ibm.com>,
	lsf-pc@lists.linux-foundation.org, Linux-MM <linux-mm@kvack.org>,
	linux-kernel@vger.kernel.org
Subject: Re: [LSF/MM TOPIC] Using XArray to manage the VMA
Date: Thu, 14 Mar 2019 09:43:43 -0700	[thread overview]
Message-ID: <20190314164343.owsgnldxk7qr363q@linux-r8p5> (raw)
In-Reply-To: <20190314023910.GL19508@bombadil.infradead.org>

On Wed, 13 Mar 2019, Matthew Wilcox wrote:

>It's probably worth listing the advantages of the Maple Tree over the
>rbtree.

I'm not familiar with maple trees, are they referred to by another name?
(is this some sort of B-tree?). Google just shows me real trees.

>
> - Shallower tree.  A 1000-entry rbtree is 10 levels deep.  A 1000-entry
>   Maple Tree is 5 levels deep (I did a more detailed analysis in an
>   earlier email thread with Laurent and I can present it if needed).

I'd be interested in reading on that.

> - O(1) prev/next
> - Lookups under the RCU lock
>
>There're some second-order effects too; by using externally allocated
>nodes, we avoid disturbing other VMAs when inserting/deleting, and we
>avoid bouncing cachelines around (eg the VMA which happens to end up
>at the head of the tree is accessed by every lookup in the tree because
>it's on the way to every other node).

How would maple trees deal with the augmented vma tree (vma gaps) trick
we use to optimize get_unmapped_area?

Thanks,
Davidlohr

  reply	other threads:[~2019-03-14 16:43 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-03-13 15:10 [LSF/MM TOPIC] Using XArray to manage the VMA Laurent Dufour
2019-03-13 18:01 ` Matthew Wilcox
2019-03-29  9:31   ` Laurent Dufour
2019-03-13 21:06 ` Davidlohr Bueso
2019-03-14  2:39   ` Matthew Wilcox
2019-03-14 16:43     ` Davidlohr Bueso [this message]
2019-03-14 19:54       ` Matthew Wilcox

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