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 8F964C001E0 for ; Thu, 10 Aug 2023 00:10:33 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231229AbjHJAKc (ORCPT ); Wed, 9 Aug 2023 20:10:32 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41648 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230263AbjHJAKa (ORCPT ); Wed, 9 Aug 2023 20:10:30 -0400 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 7DC5410C7 for ; Wed, 9 Aug 2023 17:09:44 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1691626183; 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=RhYjGeDQjHaify9fYveKNlg3W8+1+0vVy9IFYKIMw0M=; b=TmcJYfCnmq5zm2wFuGcK6rUmvlVg3sl4aFa4zHaQ07CgaJElz1jsrwAHeWA1/uDfmIMaHH fGArd4a4vA6Efd7mstjHs7u0Br+8rdqXQOgoElYrgCudRx+zM5HZ/JvFZ1ckxkxLYI4mh1 ODS/lnFKoMPRb7ik0mlhQQ/hYsuCOAc= Received: from mimecast-mx02.redhat.com (66.187.233.73 [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-583-dBjPouXWOO-yZ4G5_5ahoA-1; Wed, 09 Aug 2023 20:09:40 -0400 X-MC-Unique: dBjPouXWOO-yZ4G5_5ahoA-1 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.rdu2.redhat.com [10.11.54.4]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 0557D3802BBC; Thu, 10 Aug 2023 00:09:40 +0000 (UTC) Received: from fedora (unknown [10.72.120.3]) by smtp.corp.redhat.com (Postfix) with ESMTPS id EA7C02026D4B; Thu, 10 Aug 2023 00:09:32 +0000 (UTC) Date: Thu, 10 Aug 2023 08:09:27 +0800 From: Ming Lei To: Christoph Hellwig Cc: Jens Axboe , linux-nvme@lists.infradead.org, "Martin K . Petersen" , linux-scsi@vger.kernel.org, linux-block@vger.kernel.org, Wen Xiong , Keith Busch , linuxppc-dev@lists.ozlabs.org, Dave Young , kexec@lists.infradead.org, linux-kernel@vger.kernel.org, Baoquan He , Pingfan Liu Subject: Re: [PATCH V3 01/14] blk-mq: add blk_mq_max_nr_hw_queues() Message-ID: References: <20230808104239.146085-1-ming.lei@redhat.com> <20230808104239.146085-2-ming.lei@redhat.com> <20230809134401.GA31852@lst.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230809134401.GA31852@lst.de> X-Scanned-By: MIMEDefang 3.1 on 10.11.54.4 Precedence: bulk List-ID: X-Mailing-List: linux-scsi@vger.kernel.org On Wed, Aug 09, 2023 at 03:44:01PM +0200, Christoph Hellwig wrote: > I'm starting to sound like a broken record, but we can't just do random > is_kdump checks, and it's not going to get better by resending it again and > again. If kdump kernels limit the number of possible CPUs, it needs to > reflected in cpu_possible_map and we need to use that information. > Can you look at previous kdump/arch guys' comment about kdump usage & num_possible_cpus? https://lore.kernel.org/linux-block/CAF+s44RuqswbosY9kMDx35crviQnxOeuvgNsuE75Bb0Y2Jg2uw@mail.gmail.com/ https://lore.kernel.org/linux-block/ZKz912KyFQ7q9qwL@MiWiFi-R3L-srv/ The point is that kdump kernels does not limit the number of possible CPUs. 1) some archs support 'nr_cpus=1' for kdump kernel, which is fine, since num_possible_cpus becomes 1. 2) some archs do not support 'nr_cpus=1', and have to rely on 'max_cpus=1', so num_possible_cpus isn't changed, and kernel just boots with single online cpu. That causes trouble because blk-mq limits single queue. Documentation/admin-guide/kdump/kdump.rst Thanks, Ming