linux-kernel - RE: [PATCH] vfs: keep inodes with page cache off the inode shrinker LRU

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Message-ID: <TYAPR01MB2285608AFEB9D1FC7AB10E41B7130@TYAPR01MB2285.jpnprd01.prod.outlook.com>
Date:   Thu, 20 Feb 2020 14:35:13 +0000
From:   Chris Paterson <Chris.Paterson2@...esas.com>
To:     Arnd Bergmann <arnd@...db.de>
CC:     Geert Uytterhoeven <geert@...ux-m68k.org>,
        Russell King - ARM Linux admin <linux@...linux.org.uk>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Michal Hocko <mhocko@...e.com>,
        Rik van Riel <riel@...riel.com>,
        Catalin Marinas <catalin.marinas@....com>,
        "kernel-team@...com" <kernel-team@...com>,
        Dave Chinner <david@...morbit.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux-MM <linux-mm@...ck.org>,
        Yafang Shao <laoar.shao@...il.com>,
        Al Viro <viro@...iv.linux.org.uk>,
        Johannes Weiner <hannes@...xchg.org>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Roman Gushchin <guro@...com>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        Kishon Vijay Abraham I <kishon@...com>,
        Santosh Shilimkar <ssantosh@...nel.org>,
        "cip-dev@...ts.cip-project.org" <cip-dev@...ts.cip-project.org>
Subject: RE: [PATCH] vfs: keep inodes with page cache off the inode shrinker
 LRU

Hello,

> From: Arnd Bergmann <arnd@...db.de>
> Sent: 16 February 2020 20:38
> 
> On Sun, Feb 16, 2020 at 8:54 PM Chris Paterson
> <Chris.Paterson2@...esas.com> wrote:
> >
> > Hello Arnd, Geert,
> >
> > > From: Geert Uytterhoeven <geert@...ux-m68k.org>
> > > Sent: 16 February 2020 09:45
> > > To: Arnd Bergmann <arnd@...db.de>
> > >
> > > Hi Arnd,
> > >
> > > On Sat, Feb 15, 2020 at 5:59 PM Arnd Bergmann <arnd@...db.de> wrote:
> > > > On Sat, Feb 15, 2020 at 12:25 PM Geert Uytterhoeven
> > > > <geert@...ux-m68k.org> wrote:
> > > > > On Thu, Feb 13, 2020 at 5:54 PM Arnd Bergmann <arnd@...db.de>
> > > wrote:
> > > > > > On Wed, Feb 12, 2020 at 9:50 AM Russell King - ARM Linux admin
> > > > > > <linux@...linux.org.uk> wrote:
> > > > >
> > > > > The CIP-supported RZ/G1 SoCs can have up to 4 GiB, typically split
> (even
> > > > > for 1 GiB or 2 GiB configurations) in two parts, one below and one
> above
> > > > > the 32-bit physical limit.
> >
> > Yep. One example is r8a7743-iwg20m.dtsi.
> 
> This one has 2x512MB, with half above the 4GiB limit. This means it needs
> LPAE to address high physical addresses (which is fine), but it does not need
> highmem if one uses an appropriate CONFIG_VMSPLIT_* option.
> 
> > > > Good to know. I think there are several other chips that have dual-
> channel
> > > > DDR3 and thus /can/ support this configuration, but this rarely happens.
> > > > Are you aware of commercial products that use a 4GB configuration,
> aside
> > > from
> > > > the reference board?
> >
> > iWave Systems make a range of SOM modules using the RZ/G1 SoCs.
> > I believe there are options for some of these to use 4 GB, although 1 or 2
> GB is
> > used in the boards we've upstreamed support for.
> >
> > There are also other SOM vendors (e.g. Emtrion) and end users of RZ/G1,
> > but I'm not sure of the details.
> 
> Both iWave and Emtrion only seem to list boards with 2GB or less on their
> websites today (with up to 15 year availability). My guess is that they had
> the same problem as everyone else in finding the right memory chips in
> the required quantities and/or long-term availability. iWave lists "By default
> 1GB DDR3 and 4GB eMMC only supported. Contact iWave for memory
> expansion support." on some boards, but that doesn't mean they ever
> shipped a 4GB configuration.

I probably should have been clearer before - I actually have a couple of iWave RZ/G1M SOM modules with 4GB DDR on them.
However I've never booted them nor do I know what the memory mapping is.

Kind regards, Chris

> 
>        Arnd