Re: [PATCH] vfs: keep inodes with page cache off the inode shrinker LRU - Russell King

From: Russell King - ARM Linux admin <linux@armlinux.org.uk>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Michal Hocko <mhocko@suse.com>, Rik van Riel <riel@surriel.com>,
	Catalin Marinas <catalin.marinas@arm.com>,
	kernel-team@fb.com, Dave Chinner <david@fromorbit.com>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	Linux-MM <linux-mm@kvack.org>, Yafang Shao <laoar.shao@gmail.com>,
	Al Viro <viro@zeniv.linux.org.uk>,
	Johannes Weiner <hannes@cmpxchg.org>,
	linux-fsdevel <linux-fsdevel@vger.kernel.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	Roman Gushchin <guro@fb.com>,
	Linux ARM <linux-arm-kernel@lists.infradead.org>
Subject: Re: [PATCH] vfs: keep inodes with page cache off the inode shrinker LRU
Date: Wed, 12 Feb 2020 08:50:04 +0000	[thread overview]
Message-ID: <20200212085004.GL25745@shell.armlinux.org.uk> (raw)
In-Reply-To: <CAHk-=wg1ZDADD3Vuw_sXhmBOrQ2xsp8YWxmtWiA6vG0RT-ZQ+A@mail.gmail.com>

On Tue, Feb 11, 2020 at 05:03:02PM -0800, Linus Torvalds wrote:
> On Tue, Feb 11, 2020 at 4:47 PM Andrew Morton <akpm@linux-foundation.org> wrote:
> >
> > What's the situation with highmem on ARM?
> 
> Afaik it's exactly the same as highmem on x86 - only 32-bit ARM ever
> needed it, and I was ranting at some people for repeating all the
> mistakes Intel did.
> 
> But arm64 doesn't need it, and while 32-bit arm is obviosuly still
> selling, I think that in many ways the switch-over to 64-bit has been
> quicker on ARM than it was on x86. Partly because it happened later
> (so all the 64-bit teething pains were dealt with), but largely
> because everybody ended up actively discouraging 32-bit on the Android
> side.
> 
> There were a couple of unfortunate early 32-bit arm server attempts,
> but they were - predictably - complete garbage and nobody bought them.
> They don't exist any more.
> 
> So at least my gut feel is that the arm people don't have any big
> reason to push for maintaining HIGHMEM support either.
> 
> But I'm adding a couple of arm people and the arm list just in case
> they have some input.
> 
> [ Obvious background for newly added people: we're talking about
> making CONFIG_HIGHMEM a deprecated feature and saying that if you want
> to run with lots of memory on a 32-bit kernel, you're doing legacy
> stuff and can use a legacy kernel ]

Well, the recent 32-bit ARM systems generally have more than 1G
of memory, so make use of highmem as a rule.  You're probably
talking about crippling support for any 32-bit ARM system produced
in the last 8 to 10 years.

-- 
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
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