linux-kernel - Re: [PATCH 3/3] mm, lru_gen: try to prefetch next page when canning LRU

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Message-ID: <ZYmi1GEH0ai/2iGo@casper.infradead.org>
Date: Mon, 25 Dec 2023 15:42:12 +0000
From: Matthew Wilcox <willy@...radead.org>
To: Yu Zhao <yuzhao@...gle.com>
Cc: Kairui Song <kasong@...cent.com>, linux-mm@...ck.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org,
	Suren Baghdasaryan <surenb@...gle.com>
Subject: Re: [PATCH 3/3] mm, lru_gen: try to prefetch next page when canning
 LRU

On Sun, Dec 24, 2023 at 11:41:31PM -0700, Yu Zhao wrote:
> On Fri, Dec 22, 2023 at 3:24 AM Kairui Song <ryncsn@...il.com> wrote:
> >
> > From: Kairui Song <kasong@...cent.com>
> >
> > Prefetch for inactive/active LRU have been long exiting, apply the same
> > optimization for MGLRU.
> 
> I seriously doubt that prefetch helps in this case.
> 
> Willy, any thoughts on this? Thanks.

It _might_ ... highly depends on microarchitecture.  My experience is
that it offers more benefit on AMD than on Intel, but that experience
is several generations out of date and it may just not be applicable to
modern AMD.

It's probably more effective on ARM Cortex A cores than on ARM Cortex X
cores ... maybe we can get someone from Android (Suren?) to do some
testing?