From patchwork Mon Dec 28 12:46:13 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Greg KH X-Patchwork-Id: 353124 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=-23.7 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER, INCLUDES_PATCH, MAILING_LIST_MULTI, MENTIONS_GIT_HOSTING, SPF_HELO_NONE, SPF_PASS, URIBL_RED, USER_AGENT_GIT 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 60A04C43333 for ; Mon, 28 Dec 2020 16:11:45 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 3EDC720719 for ; Mon, 28 Dec 2020 16:11:45 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2388372AbgL1QLf (ORCPT ); Mon, 28 Dec 2020 11:11:35 -0500 Received: from mail.kernel.org ([198.145.29.99]:51020 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2388361AbgL1NWy (ORCPT ); Mon, 28 Dec 2020 08:22:54 -0500 Received: by mail.kernel.org (Postfix) with ESMTPSA id A2834206ED; Mon, 28 Dec 2020 13:22:37 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1609161758; bh=QfqfVDkEZadu+swJT4ZFbYm03D2i4eGeVCEs5nTdaNo=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=j8GJw0yqHZ1nHobG643+y4jGFKqkXSxYvkurDL4nGUNat0EqJlxXmMz5ohJ3rhBQg Ew6aGixtoAb7pm7CVs/jk/r4piyNIfYoNISWOrybtGVTfPNI9POKSJycfUn8y7Dx3S 7bJTsQDJq5jNUyPxhEofoT+YSjqWJY93QRHXxV/U= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Xiaochen Shen , Borislav Petkov , Tony Luck , Sudip Mukherjee Subject: [PATCH 4.19 054/346] x86/resctrl: Fix incorrect local bandwidth when mba_sc is enabled Date: Mon, 28 Dec 2020 13:46:13 +0100 Message-Id: <20201228124922.403987487@linuxfoundation.org> X-Mailer: git-send-email 2.29.2 In-Reply-To: <20201228124919.745526410@linuxfoundation.org> References: <20201228124919.745526410@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Xiaochen Shen commit 06c5fe9b12dde1b62821f302f177c972bb1c81f9 upstream The MBA software controller (mba_sc) is a feedback loop which periodically reads MBM counters and tries to restrict the bandwidth below a user-specified value. It tags along the MBM counter overflow handler to do the updates with 1s interval in mbm_update() and update_mba_bw(). The purpose of mbm_update() is to periodically read the MBM counters to make sure that the hardware counter doesn't wrap around more than once between user samplings. mbm_update() calls __mon_event_count() for local bandwidth updating when mba_sc is not enabled, but calls mbm_bw_count() instead when mba_sc is enabled. __mon_event_count() will not be called for local bandwidth updating in MBM counter overflow handler, but it is still called when reading MBM local bandwidth counter file 'mbm_local_bytes', the call path is as below: rdtgroup_mondata_show() mon_event_read() mon_event_count() __mon_event_count() In __mon_event_count(), m->chunks is updated by delta chunks which is calculated from previous MSR value (m->prev_msr) and current MSR value. When mba_sc is enabled, m->chunks is also updated in mbm_update() by mistake by the delta chunks which is calculated from m->prev_bw_msr instead of m->prev_msr. But m->chunks is not used in update_mba_bw() in the mba_sc feedback loop. When reading MBM local bandwidth counter file, m->chunks was changed unexpectedly by mbm_bw_count(). As a result, the incorrect local bandwidth counter which calculated from incorrect m->chunks is shown to the user. Fix this by removing incorrect m->chunks updating in mbm_bw_count() in MBM counter overflow handler, and always calling __mon_event_count() in mbm_update() to make sure that the hardware local bandwidth counter doesn't wrap around. Test steps: # Run workload with aggressive memory bandwidth (e.g., 10 GB/s) git clone https://github.com/intel/intel-cmt-cat && cd intel-cmt-cat && make ./tools/membw/membw -c 0 -b 10000 --read # Enable MBA software controller mount -t resctrl resctrl -o mba_MBps /sys/fs/resctrl # Create control group c1 mkdir /sys/fs/resctrl/c1 # Set MB throttle to 6 GB/s echo "MB:0=6000;1=6000" > /sys/fs/resctrl/c1/schemata # Write PID of the workload to tasks file echo `pidof membw` > /sys/fs/resctrl/c1/tasks # Read local bytes counters twice with 1s interval, the calculated # local bandwidth is not as expected (approaching to 6 GB/s): local_1=`cat /sys/fs/resctrl/c1/mon_data/mon_L3_00/mbm_local_bytes` sleep 1 local_2=`cat /sys/fs/resctrl/c1/mon_data/mon_L3_00/mbm_local_bytes` echo "local b/w (bytes/s):" `expr $local_2 - $local_1` Before fix: local b/w (bytes/s): 11076796416 After fix: local b/w (bytes/s): 5465014272 Fixes: ba0f26d8529c (x86/intel_rdt/mba_sc: Prepare for feedback loop) Signed-off-by: Xiaochen Shen Signed-off-by: Borislav Petkov Reviewed-by: Tony Luck Cc: Link: https://lkml.kernel.org/r/1607063279-19437-1-git-send-email-xiaochen.shen@intel.com [sudip: manual backport to file at old path] Signed-off-by: Sudip Mukherjee Signed-off-by: Greg Kroah-Hartman --- arch/x86/kernel/cpu/intel_rdt_monitor.c | 6 ++---- 1 file changed, 2 insertions(+), 4 deletions(-) --- a/arch/x86/kernel/cpu/intel_rdt_monitor.c +++ b/arch/x86/kernel/cpu/intel_rdt_monitor.c @@ -290,7 +290,6 @@ static void mbm_bw_count(u32 rmid, struc return; chunks = mbm_overflow_count(m->prev_bw_msr, tval); - m->chunks += chunks; cur_bw = (chunks * r->mon_scale) >> 20; if (m->delta_comp) @@ -460,15 +459,14 @@ static void mbm_update(struct rdt_domain } if (is_mbm_local_enabled()) { rr.evtid = QOS_L3_MBM_LOCAL_EVENT_ID; + __mon_event_count(rmid, &rr); /* * Call the MBA software controller only for the * control groups and when user has enabled * the software controller explicitly. */ - if (!is_mba_sc(NULL)) - __mon_event_count(rmid, &rr); - else + if (is_mba_sc(NULL)) mbm_bw_count(rmid, &rr); } }