From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 52575C77B7E for ; Tue, 2 May 2023 14:07:52 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234099AbjEBOHu (ORCPT ); Tue, 2 May 2023 10:07:50 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60524 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233614AbjEBOHs (ORCPT ); Tue, 2 May 2023 10:07:48 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id D13AC1FC9 for ; Tue, 2 May 2023 07:07:46 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 68957622C0 for ; Tue, 2 May 2023 14:07:46 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 90F29C4339E; Tue, 2 May 2023 14:07:44 +0000 (UTC) Date: Tue, 2 May 2023 15:07:41 +0100 From: Catalin Marinas To: Justin Forbes Cc: Mike Rapoport , Will Deacon , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, jmforbes@linuxtx.org, Andrew Morton Subject: Re: [PATCH] Revert arm64: drop ranges in definition of ARCH_FORCE_MAX_ORDER Message-ID: References: <20230428153646.823736-1-jforbes@fedoraproject.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, May 01, 2023 at 04:24:38PM -0500, Justin Forbes wrote: > On Sat, Apr 29, 2023 at 11:02 PM Mike Rapoport 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