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 0D2CDC433FE for ; Wed, 12 Oct 2022 20:42:52 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229887AbiJLUms (ORCPT ); Wed, 12 Oct 2022 16:42:48 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:58310 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229945AbiJLUmT (ORCPT ); Wed, 12 Oct 2022 16:42:19 -0400 Received: from mail.skyhub.de (mail.skyhub.de [5.9.137.197]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B05D210B783 for ; Wed, 12 Oct 2022 13:41:39 -0700 (PDT) Received: from zn.tnic (p200300ea9733e705329c23fffea6a903.dip0.t-ipconnect.de [IPv6:2003:ea:9733:e705:329c:23ff:fea6:a903]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.skyhub.de (SuperMail on ZX Spectrum 128k) with ESMTPSA id 0A9D91EC064C; Wed, 12 Oct 2022 22:41:13 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=alien8.de; s=dkim; t=1665607273; 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: content-transfer-encoding:in-reply-to:in-reply-to: references:references; bh=rE+ld/p5MuyBsBdPS4nma7ByO8JmhPHSjwCTmH8KlTA=; b=lqWl4BuLduJ3cJte9Z55R4LFYPgBq/itUyfWHhlFRRavXHfLWW+asqhSGbSdLQ0Symthgj EuIYudNyFi6l+MMLTCXGPYbncicbFioO5jcLU8vzlbYGr6ZQ6sUErm4kW3dHai2kYy8kGo 1yQ0Hn1VZj7rK32aWyV9Yyuvy/O+BPo= Date: Wed, 12 Oct 2022 22:41:12 +0200 From: Borislav Petkov To: Eric DeVolder Cc: Baoquan He , Oscar Salvador , Andrew Morton , david@redhat.com, linux-kernel@vger.kernel.org, x86@kernel.org, kexec@lists.infradead.org, ebiederm@xmission.com, dyoung@redhat.com, vgoyal@redhat.com, tglx@linutronix.de, mingo@redhat.com, dave.hansen@linux.intel.com, hpa@zytor.com, nramas@linux.microsoft.com, thomas.lendacky@amd.com, robh@kernel.org, efault@gmx.de, rppt@kernel.org, sourabhjain@linux.ibm.com, linux-mm@kvack.org Subject: Re: [PATCH v12 7/7] x86/crash: Add x86 crash hotplug support Message-ID: References: <53aed03e-2eed-09b1-9532-fe4e497ea47d@oracle.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <53aed03e-2eed-09b1-9532-fe4e497ea47d@oracle.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Oct 12, 2022 at 03:19:19PM -0500, Eric DeVolder wrote: > We run here QEMU with the ability for 1024 DIMM slots. QEMU, haha. What is the highest count of DIMM slots which are hotpluggable on a real, *physical* system today? Are you saying you can have 1K DIMM slots on a board? I hardly doubt that. > So, for example, 1TiB requires 1024 DIMMs of 1GiB each with 128MiB > memblocks, that results in 8K possible memory regions. So just going > to 4TiB reaches 32K memory regions. Lemme see if I understand this correctly: when a system like that crashes, you want to kdump *all* those 4TiB in a vmcore? How long would that dump take to complete? A day? IOW, how does a realistic use case of this look like - not a QEMU one? Thx. -- Regards/Gruss, Boris. https://people.kernel.org/tglx/notes-about-netiquette