From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) (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 CD61484A5E for ; Mon, 1 Jul 2024 09:16:32 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.129.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1719825394; cv=none; b=a5UtAjuvGAZqPCP52CDxeJ8r9TUbXkftN+a2WBmrZZRbqXkPyUD4O6Gsg9kCY4u523wT1c3HPRAScFUSwzwSR6oDAQ4XqGg1fKmRTt+/L/ig07GoJaLmatLUnMhodbRYDH4KlLUqsUwA+NrJtg6AXMr5LO2bSZz6yJX/nnHsEu4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1719825394; c=relaxed/simple; bh=cwp5rplcY8DjZiq1lafOEd2HSNWPSJdoC6cJyocB40Q=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=b8e0+RcWixmWLZpNOBc89YoPtd/oqgJae86PR4YviNKR7caELpnylaqGyCNbNChwlNpp9m+SOgwe3y48g4z9I35sy6jNnuNwFmWXpS/8nLbI6mlc5FJ8jkeebInWxzjQlj3hiAZWhJMYfH6iIPE4hfKwqycpFDYdZqBIiXSV2lw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none 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=cTNl0fyO; arc=none smtp.client-ip=170.10.129.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none 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="cTNl0fyO" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1719825391; 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=EDqyRdhYnb9M1XMOG4X5CSh/FJ2XKI6Btl8RCyPZq18=; b=cTNl0fyOHcEMT7X2y43m8dtIGNFEHBixrPLc+qDdEmWfP1LBMg0IU8VO1TXCTsY3x8iIcC mYNt53X9+CSRV1AH8KSPP0/YxO+7qloVBkftCyKXeNbzeWseRkJlvMo7GoxPAkvqI+sFWy 1kwt37Gt8IhOptrV5aVKNLlXMa8itYI= Received: from mx-prod-mc-04.mail-002.prod.us-west-2.aws.redhat.com (ec2-54-186-198-63.us-west-2.compute.amazonaws.com [54.186.198.63]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-177-NPstdspGOHmTb05q43_i_A-1; Mon, 01 Jul 2024 05:16:28 -0400 X-MC-Unique: NPstdspGOHmTb05q43_i_A-1 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-04.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id BFCFB19560AD; Mon, 1 Jul 2024 09:16:25 +0000 (UTC) Received: from fedora (unknown [10.72.112.45]) by mx-prod-int-02.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 85E941956089; Mon, 1 Jul 2024 09:16:16 +0000 (UTC) Date: Mon, 1 Jul 2024 17:16:11 +0800 From: Ming Lei To: Hannes Reinecke Cc: Daniel Wagner , Jens Axboe , Keith Busch , Sagi Grimberg , Thomas Gleixner , Christoph Hellwig , Frederic Weisbecker , Mel Gorman , Sridhar Balaraman , "brookxu.cn" , linux-kernel@vger.kernel.org, linux-block@vger.kernel.org, linux-nvme@lists.infradead.org Subject: Re: [PATCH v2 3/3] lib/group_cpus.c: honor housekeeping config when grouping CPUs Message-ID: References: <20240627-isolcpus-io-queues-v2-0-26a32e3c4f75@suse.de> <20240627-isolcpus-io-queues-v2-3-26a32e3c4f75@suse.de> <0d8a5256-9719-45c5-b098-237b5a82fd36@suse.de> 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: <0d8a5256-9719-45c5-b098-237b5a82fd36@suse.de> X-Scanned-By: MIMEDefang 3.0 on 10.30.177.15 On Mon, Jul 01, 2024 at 10:43:14AM +0200, Hannes Reinecke wrote: > On 7/1/24 09:21, Ming Lei wrote: > > On Mon, Jul 01, 2024 at 09:08:32AM +0200, Daniel Wagner wrote: > > > On Sun, Jun 30, 2024 at 09:39:59PM GMT, Ming Lei wrote: > > > > > Make group_cpus_evenly aware of isolcpus configuration and use the > > > > > housekeeping CPU mask as base for distributing the available CPUs into > > > > > groups. > > > > > > > > > > Fixes: 11ea68f553e2 ("genirq, sched/isolation: Isolate from handling managed interrupts") > > > > > > > > isolated CPUs are actually handled when figuring out irq effective mask, > > > > so not sure how commit 11ea68f553e2 is wrong, and what is fixed in this > > > > patch from user viewpoint? > > > > > > IO queues are allocated/spread on the isolated CPUs and if there is an > > > thread submitting IOs from an isolated CPU it will cause noise on the > > > isolated CPUs. The question is this a use case you need/want to support? > > > > I have talked RH Openshift team weeks ago and they have such usage. > > > > userspace is free to run any application from isolated CPUs via 'taskset > > -c' even though 'isolcpus=' is passed from command line. > > > > Kernel can not add such new constraint on userspace. > > > > > We have customers who are complaining that even with isolcpus provided > > > they still see IO noise on the isolated CPUs. > > > > That is another issue, which has been fixed by the following patch: > > > > a46c27026da1 blk-mq: don't schedule block kworker on isolated CPUs > > > Hmm. Just when I thought I understood the issue ... > > How is this supposed to work, then, given that I/O can be initiated > from the isolated CPUs? > I would have accepted that we have two scheduling domains, blk-mq is > spread across all cpus, and the blk-mq cpusets are arranged according > to the isolcpu settings. > Then we can initiate I/O from the isolated cpus, and the scheduler > would 'magically' ensure that everything is only run on isolated cpus. blk-mq issues IO either from current context or kblockd context. > > But that patch would completely counteract such a setup, as during > I/O we more often than not will invoke kblockd, which then would cause > cross-talk on non-isolated cpus. If IO is submitted from isolated CPU, blk-mq will issue this IO via unbound kblockd WQ, which is guaranteed to not run on isolated CPUs. Thanks, Ming