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 2EFE5C00528 for ; Mon, 24 Jul 2023 15:48:29 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231150AbjGXPs2 (ORCPT ); Mon, 24 Jul 2023 11:48:28 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:59874 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229495AbjGXPs1 (ORCPT ); Mon, 24 Jul 2023 11:48:27 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B36E68E; Mon, 24 Jul 2023 08:48:26 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 5129161214; Mon, 24 Jul 2023 15:48:26 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 6062DC433C9; Mon, 24 Jul 2023 15:48:25 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1690213705; bh=BnR8p0NTli1iiWv9Tj8n06sGq3rdMDNYDQt3cb8Gkno=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=09knLTUNb7IDYFLoq8gfZtCz8sVHyS9i/6s6my6RY4QsUcEacAIvE5y0wBxD8x/kh ZHwQm0PleT5vwAkgR6ASkAc8XYGRrWukuQ8akak1iB+jYw8733wpkFW3PfpcbT1TB4 82SjKZ7oYXAU2etqIVWBzXQAIs+4dKYqZ+JhFs2Q= Date: Mon, 24 Jul 2023 17:48:22 +0200 From: Greg KH To: Phil Elwell Cc: axboe@kernel.dk, andres@anarazel.de, asml.silence@gmail.com, david@fromorbit.com, hch@lst.de, io-uring@vger.kernel.org, LKML , linux-xfs@vger.kernel.org, stable Subject: Re: [PATCH] io_uring: Use io_schedule* in cqring wait Message-ID: <2023072438-aftermath-fracture-3dff@gregkh> References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: io-uring@vger.kernel.org On Mon, Jul 24, 2023 at 04:35:43PM +0100, Phil Elwell wrote: > Hi Andres, > > With this commit applied to the 6.1 and later kernels (others not > tested) the iowait time ("wa" field in top) in an ARM64 build running > on a 4 core CPU (a Raspberry Pi 4 B) increases to 25%, as if one core > is permanently blocked on I/O. The change can be observed after > installing mariadb-server (no configuration or use is required). After > reverting just this commit, "wa" drops to zero again. This has been discussed already: https://lore.kernel.org/r/12251678.O9o76ZdvQC@natalenko.name It's not a bug, mariadb does have pending I/O, so the report is correct, but the CPU isn't blocked at all. thanks, greg k-h