From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from gentwo.org (gentwo.org [62.72.0.81]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 3AEF59475; Tue, 6 Aug 2024 01:03:36 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=62.72.0.81 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1722906218; cv=none; b=OncdVSGjfYi5K3gHPzPA9Oc/PeVQ9Pba3oKPog33BRFx52liSJRAlIiBLzXEzb2lVeBHYsu/O2Rm/lQa8V648jXCbXzHF0+jy7qhxd9d1QFzRSqde7Dl1XHeNPTXKpYtsdgtMXXz51j0DjKuoxX32n+vxSIO8TKY4KOYlC62eV8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1722906218; c=relaxed/simple; bh=mI9/CNrBD5qXZqkW6Ldkif5sH8/bXop/GckPD/gd55A=; h=Date:From:To:cc:Subject:In-Reply-To:Message-ID:References: MIME-Version:Content-Type; b=ZuCeJ+FdPyd9bPcDg0mBo9GEpGbC/fx0/xxqkPzEhRrZULw7W1I2MK4UeInaRjoO8Ra5b85qrr8mwUEJoq8DwNRgx4Bugq+1layBDGU5AnonlWo/4vAtPB3PsaDqvEg77abNYoQqDIJi/gE8gI32t3OZX4C5JHPRfl2VXR98aR4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=gentwo.org; spf=pass smtp.mailfrom=gentwo.org; dkim=pass (1024-bit key) header.d=gentwo.org header.i=@gentwo.org header.b=QQ8tldQY; arc=none smtp.client-ip=62.72.0.81 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=gentwo.org Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gentwo.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=gentwo.org header.i=@gentwo.org header.b="QQ8tldQY" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=gentwo.org; s=default; t=1722899398; bh=mI9/CNrBD5qXZqkW6Ldkif5sH8/bXop/GckPD/gd55A=; h=Date:From:To:cc:Subject:In-Reply-To:References:From; b=QQ8tldQYNuBdPn9xY6a20azTd0sdwHKhcR/eapjZTCzSNoTpabS307v8Ygb81en/Z mat7wjips2JSHK5yyI2pW8jghlQzeBFDTfTZWLdjFQIsgQUURJF6S3GXi0afZPMc+Y fSNRclbuyOYsljB1FCyCO8BjzSTlkteUdDh/grdY= Received: by gentwo.org (Postfix, from userid 1003) id 1DF9840402; Mon, 5 Aug 2024 16:09:58 -0700 (PDT) Received: from localhost (localhost [127.0.0.1]) by gentwo.org (Postfix) with ESMTP id 1AB86401CA; Mon, 5 Aug 2024 16:09:58 -0700 (PDT) Date: Mon, 5 Aug 2024 16:09:58 -0700 (PDT) From: "Christoph Lameter (Ampere)" To: Ankur Arora cc: linux-pm@vger.kernel.org, kvm@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, catalin.marinas@arm.com, will@kernel.org, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, x86@kernel.org, hpa@zytor.com, pbonzini@redhat.com, wanpengli@tencent.com, vkuznets@redhat.com, rafael@kernel.org, daniel.lezcano@linaro.org, peterz@infradead.org, arnd@arndb.de, lenb@kernel.org, mark.rutland@arm.com, harisokn@amazon.com, mtosatti@redhat.com, sudeep.holla@arm.com, misono.tomohiro@fujitsu.com, joao.m.martins@oracle.com, boris.ostrovsky@oracle.com, konrad.wilk@oracle.com Subject: Re: [PATCH v6 02/10] cpuidle: rename ARCH_HAS_CPU_RELAX to ARCH_HAS_OPTIMIZED_POLL In-Reply-To: <20240726201332.626395-3-ankur.a.arora@oracle.com> Message-ID: <43b24caf-2ade-e229-21f4-8c01a47f37ed@gentwo.org> References: <20240726201332.626395-1-ankur.a.arora@oracle.com> <20240726201332.626395-3-ankur.a.arora@oracle.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII; format=flowed On Fri, 26 Jul 2024, Ankur Arora wrote: > However, recent changes in poll_idle() mean that a higher level > primitive -- smp_cond_load_relaxed() is used for polling. This would > in-turn use cpu_relax() or an architecture specific implementation. Maybe explain here that smp_cond_load_relaxed will potentially wait for important events such as a cacheline changing. Thereby making the busy poll unnecessary and optimizing power use.