From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from casper.infradead.org (casper.infradead.org [90.155.50.34]) (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 E17EA2560 for ; Thu, 22 Sep 2022 08:17:50 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=qFznKR8LE1hs5qx50v8ZXbR+2FR7aIXxVNAOIFHaJP0=; b=YrrcmJKNHKRAJseBmsEUuL5P3G tfTSPLqLeBO5/WHziL3uhgDlFMhOTjewoCtJnvnm6bdXdgbH0xr1d+fTXzDrom99AjhX+LT0V+AcL 0xZC/tXBVWZmm+0O3PAC+Piucm3c27rkwOYeiRXVsa9gIxoL0JcOI5iVr0/uHa28/Gtovc3QLM/Wp GWT1bUpF3x/83YfLRs4nZW9i6azPMdGfQy+gNAoBsr/RQ2jBi7V7R9+vBfo4jt+qm+mq9apy5OORX 7RBPsus6LHbfNubhkk64o8Xtw+Y1YCjdrXjA3mq5T5NCoDdGA+4a4T2bJHHrU8T1vxXguuxsEXk4I iOuArs4g==; Received: from j130084.upc-j.chello.nl ([24.132.130.84] helo=noisy.programming.kicks-ass.net) by casper.infradead.org with esmtpsa (Exim 4.94.2 #2 (Red Hat Linux)) id 1obHOP-006s1C-U4; Thu, 22 Sep 2022 08:17:10 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits)) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id 8C4413001FD; Thu, 22 Sep 2022 10:17:05 +0200 (CEST) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 3A529200FBDFB; Thu, 22 Sep 2022 10:17:05 +0200 (CEST) Date: Thu, 22 Sep 2022 10:17:05 +0200 From: Peter Zijlstra To: Borislav Petkov Cc: K Prateek Nayak , linux-kernel@vger.kernel.org, rafael@kernel.org, lenb@kernel.org, linux-acpi@vger.kernel.org, linux-pm@vger.kernel.org, dave.hansen@linux.intel.com, tglx@linutronix.de, andi@lisas.de, puwen@hygon.cn, mario.limonciello@amd.com, rui.zhang@intel.com, gpiccoli@igalia.com, daniel.lezcano@linaro.org, ananth.narayan@amd.com, gautham.shenoy@amd.com, Calvin Ong , stable@vger.kernel.org, regressions@lists.linux.dev Subject: Re: [PATCH] ACPI: processor_idle: Skip dummy wait for processors based on the Zen microarchitecture Message-ID: References: <20220921063638.2489-1-kprateek.nayak@amd.com> Precedence: bulk X-Mailing-List: regressions@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Wed, Sep 21, 2022 at 09:48:13PM +0200, Borislav Petkov wrote: > On Wed, Sep 21, 2022 at 05:00:35PM +0200, Peter Zijlstra wrote: > > On Wed, Sep 21, 2022 at 12:06:38PM +0530, K Prateek Nayak wrote: > > > Processors based on the Zen microarchitecture support IOPORT based deeper > > > C-states. > > > > I've just gotta ask; why the heck are you using IO port based idle > > states in 2022 ?!?! You have have MWAIT, right? > > They have both. And both is Intel technology. And as I'm sure you > know AMD can't do their own thing - they kinda have to follow Intel. > Unfortunately. > > Are you saying modern Intel chipsets don't do IO-based C-states anymore? I've no idea what they do, but Linux exclusively uses MWAIT on Intel as per intel_idle.c. MWAIT also cuts down on IPIs because it wakes from the TIF write.