From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) (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 5A82528A3E1 for ; Mon, 7 Jul 2025 07:45:02 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.133.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1751874303; cv=none; b=B2W8u1uaxkHqxwesIDUPqFrBGbHuUl/A1jg27fLs2sa/QI9R+TmkPuuLAdNQPASZSYapNarGLitrqoe3HVtHXqf/lbmD0iPMOic6cuRQYY1jFhGuLn7rZCX8eYpD8xhGNFwpg3Ywe+8juJrkTl6IniVUS7BJGrPkM38azUWZpmQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1751874303; c=relaxed/simple; bh=yK4aIwKsyQJ35dvSsCmxtiNLfyzf0Pq1Pic5u+EzrNY=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=KglTeprEOFxmFJpg0Q/vBTMAivjOmKPEbOP2R5rhP85prxH2ZNFFUMxiW0XEvMBoS6DFHfShbMJgKPixi5vIdQAmfK+BTVQpI0Pj6o9ph/5urVOcBr/SogVuG7XgzH7CC6jBHPS7VWjlBk/iJUY2LsPn00zIvnqCXX8R4psyzsw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=M3hXKwsB; arc=none smtp.client-ip=170.10.133.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="M3hXKwsB" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1751874301; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=OalrTZVgCTcY8CfgCXR2MxPAgz7dMXIrKso6Jipbb5U=; b=M3hXKwsBbcPh/m1yaED/F8CxXK0Qgan7IyHBaxL3j7j3ruOCqbzFyRVPV09igBJrVsaQ4M cMttRfpa1+xQisn0ey9clM+NF8zdy7jf0YbMdsDD0UmatAJRYBbAYWFTy/FBH5rERAC2hY ivf3MhTnpuI486M0rpWRh+8NAmOFQtU= Received: from mx-prod-mc-06.mail-002.prod.us-west-2.aws.redhat.com (ec2-35-165-154-97.us-west-2.compute.amazonaws.com [35.165.154.97]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-282-ZccoFHbxPKqYGcrylrjfjg-1; Mon, 07 Jul 2025 03:44:54 -0400 X-MC-Unique: ZccoFHbxPKqYGcrylrjfjg-1 X-Mimecast-MFC-AGG-ID: ZccoFHbxPKqYGcrylrjfjg_1751874292 Received: from mx-prod-int-02.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-02.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.15]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-06.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 60B6F1801211; Mon, 7 Jul 2025 07:44:50 +0000 (UTC) Received: from fedora (unknown [10.72.116.160]) by mx-prod-int-02.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 0525F1956087; Mon, 7 Jul 2025 07:44:35 +0000 (UTC) Date: Mon, 7 Jul 2025 15:44:30 +0800 From: Ming Lei To: Daniel Wagner Cc: Jens Axboe , Keith Busch , Christoph Hellwig , Sagi Grimberg , "Michael S. Tsirkin" , Aaron Tomlin , "Martin K. Petersen" , Thomas Gleixner , Costa Shulyupin , Juri Lelli , Valentin Schneider , Waiman Long , Frederic Weisbecker , Mel Gorman , Hannes Reinecke , Mathieu Desnoyers , linux-kernel@vger.kernel.org, linux-block@vger.kernel.org, linux-nvme@lists.infradead.org, megaraidlinux.pdl@broadcom.com, linux-scsi@vger.kernel.org, storagedev@microchip.com, virtualization@lists.linux.dev, GR-QLogic-Storage-Upstream@marvell.com Subject: Re: [PATCH v7 09/10] blk-mq: prevent offlining hk CPUs with associated online isolated CPUs Message-ID: References: <20250702-isolcpus-io-queues-v7-0-557aa7eacce4@kernel.org> <20250702-isolcpus-io-queues-v7-9-557aa7eacce4@kernel.org> Precedence: bulk X-Mailing-List: virtualization@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: <20250702-isolcpus-io-queues-v7-9-557aa7eacce4@kernel.org> X-Scanned-By: MIMEDefang 3.0 on 10.30.177.15 On Wed, Jul 02, 2025 at 06:33:59PM +0200, Daniel Wagner wrote: > When isolcpus=io_queue is enabled, and the last housekeeping CPU for a > given hctx goes offline, there would be no CPU left to handle I/O. To > prevent I/O stalls, prevent offlining housekeeping CPUs that are still > serving isolated CPUs. > > When isolcpus=io_queue is enabled and the last housekeeping CPU > for a given hctx goes offline, no CPU would be left to handle I/O. > To prevent I/O stalls, disallow offlining housekeeping CPUs that are > still serving isolated CPUs. If you do so, cpu offline is failed, and this change is user visible, please document the cpu offline failure limit on Documentation/admin-guide/kernel-parameters.txt. in the next patch. Thanks, Ming