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

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Message-ID: <CAJuCfpGvWimikdpOMuRuNisR3sas9ek7Y_2fCPe706PJ6y57+g@mail.gmail.com>
Date: Tue, 26 Dec 2023 14:12:09 -0800
From: Suren Baghdasaryan <surenb@...gle.com>
To: Matthew Wilcox <willy@...radead.org>
Cc: Yu Zhao <yuzhao@...gle.com>, Kairui Song <kasong@...cent.com>, linux-mm@...ck.org, 
	Andrew Morton <akpm@...ux-foundation.org>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/3] mm, lru_gen: try to prefetch next page when canning LRU

On Mon, Dec 25, 2023 at 7:42 AM Matthew Wilcox <willy@...radead.org> wrote:
>
> 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 is several generations out of date and it may just not be applicable to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?

Android is quite noisy and I'm afraid a small improvement like this
would not be distinguishable from noise unless it's much more
pronounced. I'll take a stab but don't hold your breath.