linux-kernel - RE: [PATCH v2] zswap: replace RB tree with xarray

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Message-ID: <26e77602326d4e169a9484314cac2465@AcuMS.aculab.com>
Date: Fri, 1 Mar 2024 21:58:43 +0000
From: David Laight <David.Laight@...LAB.COM>
To: 'Chris Li' <chrisl@...nel.org>, Andrew Morton <akpm@...ux-foundation.org>
CC: "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>, Yosry Ahmed
	<yosryahmed@...gle.com>, Nhat Pham <nphamcs@...il.com>, Johannes Weiner
	<hannes@...xchg.org>, "Matthew Wilcox (Oracle)" <willy@...radead.org>,
	Chengming Zhou <zhouchengming@...edance.com>, Barry Song
	<v-songbaohua@...o.com>
Subject: RE: [PATCH v2] zswap: replace RB tree with xarray

From: Chris Li
> Sent: 29 February 2024 08:46
> 
> Very deep RB tree requires rebalance at times. That
> contributes to the zswap fault latencies. Xarray does not
> need to perform tree rebalance. Replacing RB tree to xarray
> can have some small performance gain.
> 
> One small difference is that xarray insert might fail with
> ENOMEM, while RB tree insert does not allocate additional
> memory.

What is the difference in kernel memory use?
IIRC someone pointed out (in the rosebush thread) that xarray
uses a lot of kernel memory if the items are randomly distributed.

	David

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