From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from desiato.infradead.org (desiato.infradead.org [90.155.92.199]) (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 95FCC1591EA; Wed, 24 Apr 2024 10:01:31 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=90.155.92.199 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1713952894; cv=none; b=fkaEaqkXYeG1LNxpGTztdE6LXpMQ3uklavVIdABBhDnIQM7hT8Y/R5Cts8Ag4k0aJ0HmIkmzb3sYF2vrM6HcqF4gurpABoVJ377+QJIwNKGvIFBvhJjBgcVvSvTZAYMLG2oddS2Md/a9FvlIUrXbAve4n2B72OJR+MKwPAur2Yg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1713952894; c=relaxed/simple; bh=Fu/fHJcsiVtfVkreqiB5Ns+D3AaA90LaGc5UDwmbTdQ=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=q4Gb7ESnYd9ZG38bQIvHrjV8duaLRmov4qBjyU9f//nGrL1bf9YeI08GCojzvm+IjkzeyzERcB7JTHkNZWaDtnHMOgWBNVgukyR4XG4qr/PjXxQ93ORJ2XSttOL5gHr08W3PIL741ThFra3bY4tcAWQuzXJlnjkzE+dJJiGDFW4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org; spf=none smtp.mailfrom=infradead.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b=PCUqQo7+; arc=none smtp.client-ip=90.155.92.199 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=infradead.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="PCUqQo7+" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=desiato.20200630; 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=Fu/fHJcsiVtfVkreqiB5Ns+D3AaA90LaGc5UDwmbTdQ=; b=PCUqQo7+jBxk1uOoTa31K/5TTU JlpzIdnBDmQ8ymnqMSvTFOpbczpPihRtk6/6D9STocf+bOoV8LjEpVX3wHa/OgC02wbgHT63hOw7g jyc6sUUwslpnA7fvnsKH8D/qIXo4GEMN3Z3YJjVCrK6fS5VtlNVF8vP0znXiuZGGEx9bEi17MfRzW HDWizgMSfzt8ngkgtoLoHguwgbGNACXwjG++/JRmouL4x7j0qJnU/wldwqv5gT7zO3rCJe8DXx7Ot 1yyvjgXDhv5EzUGyTsWTEAwHjBmM3fjuoUP+dkN2uQEmE6ZgBGcZMDtQNIKVk6kYQ6yQgrz7p/zWD ldlitDfg==; Received: from j130084.upc-j.chello.nl ([24.132.130.84] helo=noisy.programming.kicks-ass.net) by desiato.infradead.org with esmtpsa (Exim 4.97.1 #2 (Red Hat Linux)) id 1rzZRP-0000000ELwK-3jWq; Wed, 24 Apr 2024 10:01:28 +0000 Received: by noisy.programming.kicks-ass.net (Postfix, from userid 1000) id 871FF30043E; Wed, 24 Apr 2024 12:01:27 +0200 (CEST) Date: Wed, 24 Apr 2024 12:01:27 +0200 From: Peter Zijlstra To: Jens Axboe Cc: linux-kernel@vger.kernel.org, tglx@linutronix.de, "Rafael J. Wysocki" , linux-pm@vger.kernel.org, daniel.lezcano@linaro.org Subject: Re: [PATCH 4/4] sched/core: split iowait state into two states Message-ID: <20240424100127.GV40213@noisy.programming.kicks-ass.net> References: <20240416121526.67022-1-axboe@kernel.dk> <20240416121526.67022-5-axboe@kernel.dk> 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 Content-Disposition: inline In-Reply-To: <20240416121526.67022-5-axboe@kernel.dk> On Tue, Apr 16, 2024 at 06:11:21AM -0600, Jens Axboe wrote: > iowait is a bogus metric, but it's helpful in the sense that it allows > short waits to not enter sleep states that have a higher exit latency > than would've otherwise have been picked for iowait'ing tasks. However, > it's harmless in that lots of applications and monitoring assumes that > iowait is busy time, or otherwise use it as a health metric. > Particularly for async IO it's entirely nonsensical. Let me get this straight, all of this is about working around cpuidle menu governor insaity? Rafael, how far along are we with fully deprecating that thing? Yes it still exists, but should people really be using it still?