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 X-Spam-Level: X-Spam-Status: No, score=-2.3 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_MUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 734CAC43381 for ; Tue, 26 Feb 2019 13:54:36 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 3F25F21841 for ; Tue, 26 Feb 2019 13:54:36 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="U+fyuYgI" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727699AbfBZNye (ORCPT ); Tue, 26 Feb 2019 08:54:34 -0500 Received: from merlin.infradead.org ([205.233.59.134]:52640 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727520AbfBZNye (ORCPT ); Tue, 26 Feb 2019 08:54:34 -0500 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=merlin.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=ApI7uZCGExBqpKLg2Rlr6XR9LkoMfgsFnCmf0EFObto=; b=U+fyuYgIf5oUsS2fGyYUrd2Zg lx97ZPl0aIEbsOSs7f4pBFqMcFBGeOK5zoI1TWNMc6hTbYRriI7sTQ1PWlzHCuoVltlp4ArDCfs7T zbOO/kK9FpGAiQg7OQmpIVXqz266UID4V8cDRxRW8x4OKy6w3F5Rc242hGAQXztB/T68rkM+ihaKw BMaYqu29wxIqA+JoXgm2+U+sCBdeEf4n2z0cTfnzUs2AFeogC1XorWUsOgkjMlAlHlmPyYEyaL7sH Uow/Ac9JdTO1EQgU40b25AM3iuPNicG39AYdsYY9pUXV+qKyX9QX+LLuMOoet1R5Xv/p7xyT0ItHJ 0jICfgnpg==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=hirez.programming.kicks-ass.net) by merlin.infradead.org with esmtpsa (Exim 4.90_1 #2 (Red Hat Linux)) id 1gydBl-0006EI-1d; Tue, 26 Feb 2019 13:54:29 +0000 Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 7908F20269AFA; Tue, 26 Feb 2019 14:54:26 +0100 (CET) Date: Tue, 26 Feb 2019 14:54:26 +0100 From: Peter Zijlstra To: Len Brown Cc: X86 ML , linux-kernel@vger.kernel.org, Len Brown , linux-doc@vger.kernel.org Subject: Re: [PATCH 03/11] x86 topology: Add CPUID.1F multi-die/package support Message-ID: <20190226135426.GU32477@hirez.programming.kicks-ass.net> References: <635b2bf8b1151a191cd9299276b75791a818c0c2.1550545163.git.len.brown@intel.com> <07d2908dc72bf964b27380999e1c826587d69136.1550545163.git.len.brown@intel.com> <20190220105542.GB17969@hirez.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Feb 20, 2019 at 10:08:48AM -0500, Len Brown wrote: > Thanks for the comments, Peter. I'll update the patch to address the > syntax points. (Maybe checkpatch.pl should be updated to reflect your > preferences?). Don't know about checkpatch; I ignore plenty of its output. I think tglx started a document somewhere for what tip prefers, but I'm not sure where that went. > About macros vs C. I agree with your preference. > I used macros to be consistent with the existing code, and to be as > backport friendly as possible. > (a number of distros need to pull these patches into their supported kernels) > Sure, I'm willing to write in a cosmetic-only patch, after the > functional changes are upstream. Fair enough. > > It would've been nice to have the CPUID instruction 1F leaf reference > > 3B-3.9 in the SDM, and maybe mention this here too. > > I didn't mention SDM sections because they change -- leaving stale > pointers in our commit messages. The SDM is re-published 4 times per > year. Yah, I know. Which is why I keep all SDMs. So if you say, book 3 section 8 of Jul'17, I can find it :-) > > You haven't explained, and I can't readily find it in the SDM either, > > how these topology bits relate to caches and interconnects. > > > > Will these die thingies share LLC, or will LLC be per die. Will NUMA > > span dies or not. > > Excellent question. > Cache enumeration in Leaf-4 is totally unchanged. > ACPI NUMA tables are totally unchanged. Sure; and yet Sub-NUMA-Clustering broke stuff in interesting ways. I'm trying to get a feel for how these levels will interact with all that. Before that SNC stuff, caches had never spanned NODEs (and I still think that is 'creative' at best). > From a scheduler point of view, imagine that a SKX system with 4 die > in 4 packages was mechanically re-designed so that those 4 die resided > in 2 double-sized packages. > > They may have tweaked the links between the die, but logically it is > identical and compatible, and the legacy kernel will function > properly. This example has LLC in die and yes that works. But I can imagine things like L2 in tile and L3 across tiles but within DIE and then it _might_ make sense to still consider the tile for scheduling. Another option is having the LLC off die; also not unheard of. And then there's many creative and slightly crazy ways this can all be combined :/ > So the effect of Leaf B,1F is that it defines the scope of MSRs. eg. > what processors does a die-scope MSR cover. That is why the rest of > the patch is about sysfs topology, and about package MSR scope. > > Yes, there will be more exotic MSR situations in future products -- > the first ones are pretty simple -- something called a > package-scope-MSR in the SDM today becomes a die-scope-MSR in this > generation on a multi-die/package system. Yes :-( > It also reflects how many packages appear in sysfs, and this can > effect licensing of some kinds of software. That's just plain insanity and we should not let that affect our sysfs interfaces.