From: Yosry Ahmed <yosryahmed@google.com>
To: David Laight <David.Laight@aculab.com>
Cc: "'Chris Li'" <chrisl@kernel.org>,
Andrew Morton <akpm@linux-foundation.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"linux-mm@kvack.org" <linux-mm@kvack.org>,
Nhat Pham <nphamcs@gmail.com>,
Johannes Weiner <hannes@cmpxchg.org>,
"Matthew Wilcox (Oracle)" <willy@infradead.org>,
Chengming Zhou <zhouchengming@bytedance.com>,
Barry Song <v-songbaohua@oppo.com>
Subject: Re: [PATCH v2] zswap: replace RB tree with xarray
Date: Tue, 5 Mar 2024 03:08:15 +0000 [thread overview]
Message-ID: <ZeaMn488S_xVNtAh@google.com> (raw)
In-Reply-To: <26e77602326d4e169a9484314cac2465@AcuMS.aculab.com>
On Fri, Mar 01, 2024 at 09:58:43PM +0000, David Laight wrote:
> 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.
I often thought it would be useful if there is an API for the xarray to
report how much memory it's using. For zswap, we could plumb this to a
debugfs interface or so to measure the tree usage and compare to the
rbtree. The cost is fixed with the rbtree IIUC, 3 words per zswap entry.
prev parent reply other threads:[~2024-03-05 3:08 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-02-29 8:46 [PATCH v2] zswap: replace RB tree with xarray Chris Li
2024-02-29 9:44 ` Chengming Zhou
2024-02-29 18:58 ` Chris Li
2024-03-01 7:24 ` Chengming Zhou
2024-03-01 9:38 ` Chris Li
2024-03-02 18:33 ` Chris Li
2024-03-01 21:58 ` David Laight
2024-03-01 22:33 ` Chris Li
2024-03-05 3:08 ` Yosry Ahmed [this message]
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