linux-kernel - Re: [PATCH v8 00/70] Introducing the Maple Tree

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Message-ID: <YmhUsDe+Omf2CNCS@casper.infradead.org>
Date:   Tue, 26 Apr 2022 21:23:12 +0100
From:   Matthew Wilcox <willy@...radead.org>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     Liam Howlett <liam.howlett@...cle.com>,
        "maple-tree@...ts.infradead.org" <maple-tree@...ts.infradead.org>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Yu Zhao <yuzhao@...gle.com>
Subject: Re: [PATCH v8 00/70] Introducing the Maple Tree

On Tue, Apr 26, 2022 at 01:08:57PM -0700, Andrew Morton wrote:
> On Tue, 26 Apr 2022 15:06:19 +0000 Liam Howlett <liam.howlett@...cle.com> wrote:
> > The maple tree is an RCU-safe range based B-tree designed to use modern
> > processor cache efficiently.  There are a number of places in the kernel
> 
> I think it would be helpful to expand on "a number of places". 
> Specifically which places?

The page cache would be a good place to use it once it has a few more
features to bring it up to par with the radix tree.  I can go into more
detail if you want.

In general, anywhere that's using the IDR/Radix Tree/XArray would
benefit.  The radix tree has some pretty poor space consumption
properties, particularly for anyone using the cyclic variants.

Many users of the rbtree would have better performance if converted
to the maple tree.

Ultimately, it's going to be incumbent on people who know their own
chunk of the kernel to say "Oh, yes, I can use that data structure",
rather than on Liam to go around converting everybody's code for them.