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=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=no 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 709B0C38A2A for ; Sun, 10 May 2020 17:56:31 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 3CB482080C for ; Sun, 10 May 2020 17:56:31 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 3CB482080C Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=bugs.launchpad.net Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:56370 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1jXqBi-0003ue-Ch for qemu-devel@archiver.kernel.org; Sun, 10 May 2020 13:56:30 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:41286) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1jXqAx-0002yw-3r for qemu-devel@nongnu.org; Sun, 10 May 2020 13:55:43 -0400 Received: from indium.canonical.com ([91.189.90.7]:48518) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.90_1) (envelope-from ) id 1jXqAv-0006Vg-L4 for qemu-devel@nongnu.org; Sun, 10 May 2020 13:55:42 -0400 Received: from loganberry.canonical.com ([91.189.90.37]) by indium.canonical.com with esmtp (Exim 4.86_2 #2 (Debian)) id 1jXqAt-0006wy-Ft for ; Sun, 10 May 2020 17:55:39 +0000 Received: from loganberry.canonical.com (localhost [127.0.0.1]) by loganberry.canonical.com (Postfix) with ESMTP id 6E3B12E8076 for ; Sun, 10 May 2020 17:55:39 +0000 (UTC) MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Date: Sun, 10 May 2020 17:47:11 -0000 From: Damir <1856335@bugs.launchpad.net> To: qemu-devel@nongnu.org X-Launchpad-Notification-Type: bug X-Launchpad-Bug: product=qemu; status=New; importance=Undecided; assignee=None; X-Launchpad-Bug-Information-Type: Public X-Launchpad-Bug-Private: no X-Launchpad-Bug-Security-Vulnerability: no X-Launchpad-Bug-Commenters: babumoger djdatte h-sieger X-Launchpad-Bug-Reporter: Damir (djdatte) X-Launchpad-Bug-Modifier: Damir (djdatte) References: <157625616239.22064.10423897892496347105.malonedeb@gac.canonical.com> Message-Id: <158913283187.13853.4379051209165101767.malone@gac.canonical.com> Subject: [Bug 1856335] Re: Cache Layout wrong on many Zen Arch CPUs X-Launchpad-Message-Rationale: Subscriber (QEMU) @qemu-devel-ml X-Launchpad-Message-For: qemu-devel-ml Precedence: bulk X-Generated-By: Launchpad (canonical.com); Revision="fbdff7602bd10fb883bf7e2ddcc7fd5a16f60398"; Instance="production-secrets-lazr.conf" X-Launchpad-Hash: 5dab677e8a2465240aba436206e9fccea0c1b725 Received-SPF: none client-ip=91.189.90.7; envelope-from=bounces@canonical.com; helo=indium.canonical.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/05/10 13:55:40 X-ACL-Warn: Detected OS = Linux 3.11 and newer X-Spam_score_int: -65 X-Spam_score: -6.6 X-Spam_bar: ------ X-Spam_report: (-6.6 / 5.0 requ) BAYES_00=-1.9, HEADER_FROM_DIFFERENT_DOMAINS=0.249, RCVD_IN_DNSWL_HI=-5, RCVD_IN_MSPIKE_H3=0.001, RCVD_IN_MSPIKE_WL=0.001, URIBL_BLOCKED=0.001 autolearn=_AUTOLEARN X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: Bug 1856335 <1856335@bugs.launchpad.net> Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Hello, I took a look today at the layouts when using 1950X (which previously worked, and yes, admittedly, I am using Windows / coreinfo), and any basic config (previously something simple as Sockets=3D1,Cores=3D8, Theads= =3D1 (now also Dies=3D1) worked, but now, the topology presents as if all cores share L3, and that each two cores share L1C/L1D/L2, like if they were smt-siblings. I would call this a serious regression. I don't think using Numa Nodes is an ok way to solve this (especially not when at least for 4CCX CPUs, this worked flawlessly before), as that will make numa-aware applications start taking note of numa nodes, and possibly do wierd things (plus, it introduces more configuration where it was not needed before). -- = You received this bug notification because you are a member of qemu- devel-ml, which is subscribed to QEMU. https://bugs.launchpad.net/bugs/1856335 Title: Cache Layout wrong on many Zen Arch CPUs Status in QEMU: New Bug description: AMD CPUs have L3 cache per 2, 3 or 4 cores. Currently, TOPOEXT seems to always map Cache ass if it was an 4-Core per CCX CPU, which is incorrect, and costs upwards 30% performance (more realistically 10%) in L3 Cache Layout aware applications. Example on a 4-CCX CPU (1950X /w 8 Cores and no SMT): =C2=A0=C2=A0 =C2=A0=C2=A0=C2=A0=C2=A0EPYC-IBPB =C2=A0=C2=A0=C2=A0=C2=A0AMD =C2=A0=C2=A0=C2=A0=C2=A0 In windows, coreinfo reports correctly: ****---- Unified Cache 1, Level 3, 8 MB, Assoc 16, LineSize 64 ----**** Unified Cache 6, Level 3, 8 MB, Assoc 16, LineSize 64 On a 3-CCX CPU (3960X /w 6 cores and no SMT): =C2=A0 =C2=A0=C2=A0=C2=A0=C2=A0EPYC-IBPB =C2=A0=C2=A0=C2=A0=C2=A0AMD =C2=A0=C2=A0=C2=A0=C2=A0 in windows, coreinfo reports incorrectly: ****-- Unified Cache 1, Level 3, 8 MB, Assoc 16, LineSize 64 ----** Unified Cache 6, Level 3, 8 MB, Assoc 16, LineSize 64 Validated against 3.0, 3.1, 4.1 and 4.2 versions of qemu-kvm. With newer Qemu there is a fix (that does behave correctly) in using the = dies parameter: =C2=A0 The problem is that the dies are exposed differently than how AMD does it natively, they are exposed to Windows as sockets, which means, that if you are nto a business user, you can't ever have a machine with more than two CCX (6 cores) as consumer versions of Windows only supports two sockets. (Should this be reported as a separate bug?) To manage notifications about this bug go to: https://bugs.launchpad.net/qemu/+bug/1856335/+subscriptions