From: Catalin Marinas <catalin.marinas@arm.com>
To: Justin Forbes <jforbes@fedoraproject.org>
Cc: Mike Rapoport <rppt@kernel.org>, Will Deacon <will@kernel.org>,
linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org, jmforbes@linuxtx.org,
Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [PATCH] Revert arm64: drop ranges in definition of ARCH_FORCE_MAX_ORDER
Date: Tue, 2 May 2023 15:07:41 +0100 [thread overview]
Message-ID: <ZFEZLZHBosQK9xaH@arm.com> (raw)
In-Reply-To: <CAFbkSA0O-4YgNt-7KPhvx+vhvRNc38PO8E--GVAWKVgHK-_9Mw@mail.gmail.com>
On Mon, May 01, 2023 at 04:24:38PM -0500, Justin Forbes wrote:
> On Sat, Apr 29, 2023 at 11:02 PM Mike Rapoport <rppt@kernel.org> wrote:
> > Why the default MAX_ORDER was not acceptable on arm64 server machines but
> > it is fine on, say, x86 and s390?
> > I'm not asking how you made it possible in Fedora and RHEL, I'm asking why
> > did you switch from the default order at all.
>
> Because the MAX_ORDER on aarch64 with 4K pages is more tuned to the
> needs of the average edge client, not so much those of a server class
> machine. And I get it, I would say well over 90% of the Fedora users
> running aarch64 are indeed running on a rPi or similar with a small
> memory footprint, and workloads which match that. But we do support
> and run a 4K page size aarch64 kernel on proper server class hardware,
> running typical server workloads, and RHEL has a lot more users in the
> server class than edge clients. RHEL could probably default to 64K
> pages, and most users would be happy with that. Fedora certainly could
> not.
I was talking to Marc Zyngier earlier and he reckons the need for a
higher MAX_ORDER is the GIC driver ITS allocation for Thunder-X. I'm
happy to make ARCH_MAX_ORDER higher in defconfig (12, 13?) if
CONFIG_ARCH_THUNDER. Mobile vendors won't enable this platform.
Regarding EXPERT, we could drop it and do like the other architectures
but we'll have randconfig occasionally hitting weird values that won't
build (like -1). Not sure EXPERT helps here.
--
Catalin
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next prev parent reply other threads:[~2023-05-02 14:08 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-04-28 15:36 [PATCH] Revert arm64: drop ranges in definition of ARCH_FORCE_MAX_ORDER Justin M. Forbes
2023-04-28 17:01 ` Catalin Marinas
2023-04-29 19:01 ` Mike Rapoport
2023-04-29 22:42 ` Justin Forbes
2023-04-30 3:54 ` Mike Rapoport
2023-05-01 21:24 ` Justin Forbes
2023-05-02 14:07 ` Catalin Marinas [this message]
2023-05-02 14:21 ` Marc Zyngier
2023-05-02 16:12 ` Mike Rapoport
2023-05-02 16:15 ` Mike Rapoport
2023-05-02 17:40 ` Catalin Marinas
2023-05-03 10:20 ` Catalin Marinas
2023-05-03 12:08 ` Philip Li
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