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 lists.ozlabs.org (lists.ozlabs.org [112.213.38.117]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 1EC31EB64DD for ; Thu, 10 Aug 2023 03:02:54 +0000 (UTC) Authentication-Results: lists.ozlabs.org; dkim=fail reason="signature verification failed" (1024-bit key; unprotected) header.d=redhat.com header.i=@redhat.com header.a=rsa-sha256 header.s=mimecast20190719 header.b=KIqb5lLw; dkim=fail reason="signature verification failed" (1024-bit key) header.d=redhat.com header.i=@redhat.com header.a=rsa-sha256 header.s=mimecast20190719 header.b=RDjXuGgw; dkim-atps=neutral Received: from boromir.ozlabs.org (localhost [IPv6:::1]) by lists.ozlabs.org (Postfix) with ESMTP id 4RLsDX3DxLz3cST for ; Thu, 10 Aug 2023 13:02:52 +1000 (AEST) Authentication-Results: lists.ozlabs.org; dkim=pass (1024-bit key; unprotected) header.d=redhat.com header.i=@redhat.com header.a=rsa-sha256 header.s=mimecast20190719 header.b=KIqb5lLw; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.a=rsa-sha256 header.s=mimecast20190719 header.b=RDjXuGgw; dkim-atps=neutral Authentication-Results: lists.ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=redhat.com (client-ip=170.10.133.124; helo=us-smtp-delivery-124.mimecast.com; envelope-from=bhe@redhat.com; receiver=lists.ozlabs.org) Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) (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 lists.ozlabs.org (Postfix) with ESMTPS id 4RLsCY1GZDz3bX2 for ; Thu, 10 Aug 2023 13:01:59 +1000 (AEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1691636516; 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=594nXTsTgZOwSIbiFys/fNQ4V66vIHVyVd6OCcJP7n4=; b=KIqb5lLwR/htX30FtnnACAuBpsQ/AHrNGKOdUwX5F5K41Dq/BCGuvSjMplVtv5jaIPC8YD lF9K4MYsWT6YlUTh1X7a2egoFdlN8aSxJWayVvwWcdVLhn/CT3SaOhdmHgswyDTzwCTjD2 AIP4rx92nKcUIdlyuGGuQdOoAxMBY+Y= DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1691636517; 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=594nXTsTgZOwSIbiFys/fNQ4V66vIHVyVd6OCcJP7n4=; b=RDjXuGgwkhk1/J4ymRywEEJXuZ66f6KIk0JS8vbJwmK9hel5Wq9J2YUJIKOmKCvQM18biy aB5ozSJNKo6zVmBVFiKG92npIZTWYfMUc9M4mu3k15F41zXJktw0YXG0KvaGNZoTfQjEXL G+bFb6pa+qvm9W4+RSl0RSNUJ7aoo3Y= 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-158-462o-o7QOKu_hKQjukBwpw-1; Wed, 09 Aug 2023 23:01:51 -0400 X-MC-Unique: 462o-o7QOKu_hKQjukBwpw-1 Received: from smtp.corp.redhat.com (int-mx10.intmail.prod.int.rdu2.redhat.com [10.11.54.10]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 5C5D83C01BA8; Thu, 10 Aug 2023 03:01:50 +0000 (UTC) Received: from localhost (unknown [10.72.112.99]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 6AEB7492C13; Thu, 10 Aug 2023 03:01:49 +0000 (UTC) Date: Thu, 10 Aug 2023 11:01:46 +0800 From: Baoquan He To: Ming Lei 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: X-Scanned-By: MIMEDefang 3.1 on 10.11.54.10 X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Jens Axboe , linux-scsi@vger.kernel.org, "Martin K . Petersen" , Pingfan Liu , Dave Young , npiggin@gmail.com, linux-kernel@vger.kernel.org, linux-nvme@lists.infradead.org, linux-block@vger.kernel.org, Wen Xiong , kexec@lists.infradead.org, Keith Busch , linuxppc-dev@lists.ozlabs.org, Christoph Hellwig Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On 08/10/23 at 10:06am, Ming Lei wrote: > On Thu, Aug 10, 2023 at 09:18:27AM +0800, Baoquan He wrote: > > On 08/10/23 at 08:09am, Ming Lei wrote: > > > 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. > > > > Yes, "nr_cpus=" is strongly suggested in kdump kernel because "nr_cpus=" > > limits the possible cpu numbers, while "maxcpuss=" only limits the cpu > > number which can be brought up during bootup. We noticed this diference > > because a large number of possible cpus will cost more memory in kdump > > kernel. e.g percpu initialization, even though kdump kernel have set > > "maxcpus=1". > > > > Currently x86 and arm64 all support "nr_cpus=". Pingfan ever spent much > > effort to make patches to add "nr_cpus=" support to ppc64, seems ppc64 > > dev and maintainers do not care about it. Finally the patches are not > > accepted, and the work is not continued. > > > > Now, I am wondering what is the barrier to add "nr_cpus=" to power ach. > > Can we reconsider adding 'nr_cpus=' to power arch since real issue > > occurred in kdump kernel? > > If 'nr_cpus=' can be supported on ppc64, this patchset isn't needed. > > > > > As for this patchset, it can be accpeted so that no failure in kdump > > kernel is seen on ARCHes w/o "nr_cpus=" support? My personal opinion. > > IMO 'nr_cpus=' support should be preferred, given it is annoying to > maintain two kinds of implementation for kdump kernel from driver > viewpoint. I guess kdump things can be simplified too with supporting > 'nr_cpus=' only. Yes, 'nr_cpus=' is ideal. Not sure if there's some underlying concerns so that power people decided to not support it.