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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 7FD91C88E45 for ; Fri, 11 Sep 2026 14:16:04 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:Content-Transfer-Encoding: Content-Type:In-Reply-To:From:References:Cc:To:Subject:MIME-Version:Date: Message-ID:Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=2KBZHYychmDXb/7ON1UgL8gyckYpgs6QfPENVttHvSo=; b=4twKlJW/hoP/Lc02BFwINOKFYa H8S0sv55B+g7UjhRQPZXr+yrMbhkQMYpLBsQo0TSw7tgA1YGF+aMLcLXOugRL/3tWRrTrYaOoOQKu 1UOUx2EDxrvrjnwhsf9oKK9sw1RhGlDxBJpfKeX3njr8xfmb9MIQBtfGnyYLMiKxsf+548OccEKPf GwE7IQTXX04x9EFfN81fjEa1gRIabjz3WS2PkLrOOj8h665CLK65tieppjXKf1lcPVI9nk08Rb2bb jxewgveDAl64jQcRxo0/Tu2yQVfSr9kNf0ixpJF6Gdh5IsQLJmF3KLIzfU6aZuGg1jEYn9qjmXOR8 y6jNY6BA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.99.1 #2 (Red Hat Linux)) id 1x522l-0000000Gt8P-2pSx; Fri, 11 Sep 2026 14:15:55 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.99.1 #2 (Red Hat Linux)) id 1x522f-0000000Gt7o-2Er6 for linux-arm-kernel@lists.infradead.org; Fri, 11 Sep 2026 14:15:54 +0000 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 9AD9C16F2; Fri, 11 Sep 2026 07:15:44 -0700 (PDT) Received: from [10.57.73.19] (unknown [10.57.73.19]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id B6D193F7B4; Fri, 11 Sep 2026 07:15:44 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=arm.com; s=foss; t=1789136148; bh=d6mzXbmJYFm0GynqcHkfdRTupKXChsoklSxL3P+yA9A=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=fmcup4RLpkQPrB7uRbMMbrAv43xH71VYNGkTpY8+FbNIAeNMuNklcinPYlN6V44AQ TaJ5cHe04TW8rkSnz3vYYQzfIi7N4Nf9ZWEZGjFMV1CKICVhPyJtkiHWnEAM55SduO eWCfO0AJalfAUzdhKo1Wd+i+j4Qb0aUvdYUqHgNw= Message-ID: <2646dfa6-3f0f-49d1-a7d8-4b93fbd1ec71@arm.com> Date: Fri, 11 Sep 2026 16:15:42 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 1/2] arm64: topology: Prefer PE0 on NVIDIA Olympus SMT cores To: Andrea Righi Cc: Ingo Molnar , Peter Zijlstra , Juri Lelli , Vincent Guittot , Catalin Marinas , Will Deacon , Steven Rostedt , Ben Segall , Mel Gorman , Valentin Schneider , K Prateek Nayak , Mark Rutland , Christian Loehle , Shrikanth Hegde , Phil Auld , Breno Leitao , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org References: <20260909062649.469633-1-arighi@nvidia.com> <20260909062649.469633-2-arighi@nvidia.com> <89694e14-4be8-4c9e-9d7b-2808f87dd95f@arm.com> <1528999e-eb59-416f-b18f-2a7667e61a90@arm.com> Content-Language: en-GB From: Dietmar Eggemann In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260911_071552_306666_A8F592C1 X-CRM114-Status: GOOD ( 16.62 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 11.09.26 11:11, Andrea Righi wrote: > Hi Dietmar, > > On Thu, Sep 10, 2026 at 12:11:06PM +0200, Dietmar Eggemann wrote: >> On 09.09.26 18:17, Andrea Righi wrote: >>> On Wed, Sep 09, 2026 at 05:19:08PM +0200, Dietmar Eggemann wrote: >>>> On 09.09.26 08:26, Andrea Righi wrote: [...] > I think we can avoid an arm64 override entirely and rely on the default > implementation: > > int __weak arch_asym_cpu_priority(int cpu) > { > return -cpu; > } > > The boot option would only add SD_ASYM_PACKING to the SMT domain. A rough > prototype could look like this in kernel/sched/topology.c: > > static bool sched_smt_asym_packing __read_mostly; > > static int __init setup_sched_smt_asym_packing(char *str) > { > sched_smt_asym_packing = true; > return 1; > } > __setup("sched_smt_asym_packing", setup_sched_smt_asym_packing); > > int cpu_smt_flags(void) > { > int flags = SD_SHARE_CPUCAPACITY | SD_SHARE_LLC; > > if (sched_smt_asym_packing) > flags |= SD_ASYM_PACKING; > > return flags; > } > > This would make the option generic rather than specific to arm64 or Olympus. Ah, OK, no arm64 private 'struct sched_domain_topology_level arm64_asym_smt_topology[]' anymore. [...]