From patchwork Sun Oct 8 07:23:46 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Yi Sun X-Patchwork-Id: 9991755 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id 484AF60244 for ; Sun, 8 Oct 2017 07:48:10 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 3931F28689 for ; Sun, 8 Oct 2017 07:48:10 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 2DEA928713; Sun, 8 Oct 2017 07:48:10 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-4.2 required=2.0 tests=BAYES_00, RCVD_IN_DNSWL_MED autolearn=ham version=3.3.1 Received: from lists.xenproject.org (lists.xenproject.org [192.237.175.120]) (using TLSv1.2 with cipher AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.wl.linuxfoundation.org (Postfix) with ESMTPS id 45C8428689 for ; Sun, 8 Oct 2017 07:48:09 +0000 (UTC) Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.84_2) (envelope-from ) id 1e16Gs-0002fP-Ut; Sun, 08 Oct 2017 07:45:10 +0000 Received: from mail6.bemta5.messagelabs.com ([195.245.231.135]) by lists.xenproject.org with esmtp (Exim 4.84_2) (envelope-from ) id 1e16Gs-0002fD-6z for xen-devel@lists.xenproject.org; Sun, 08 Oct 2017 07:45:10 +0000 Received: from [85.158.139.211] by server-11.bemta-5.messagelabs.com id AD/67-01772-587D9D95; Sun, 08 Oct 2017 07:45:09 +0000 X-Brightmail-Tracker: H4sIAAAAAAAAA+NgFtrHIsWRWlGSWpSXmKPExsXS1taRotty/Wa kwd1uBYvvWyYzOTB6HP5whSWAMYo1My8pvyKBNeNuz2q2gs2FFQdnL2VvYLwa1MXIySEkUCHx ccFsVhBbQoBX4siyGVB2gMTetRNZIGoaGCVmz9UAsdkE1CUef+1hArFFBJQk7q2aDGRzcTALL GOW+PhiFVizsECkxNu2v0DNHBwsAqoSi9YmgIR5Bdwlbk28zggxX07i5LHJYOWcAh4Ss85vYI fY5S6xenU7I0S9oMTJmU/AxjAD7V0/TwgkzCwgL9G8dTbzBEaBWUiqZiFUzUJStYCReRWjenF qUVlqka6hXlJRZnpGSW5iZo6uoYGpXm5qcXFiempOYlKxXnJ+7iZGYFjWMzAw7mBs6nU+xCjJ waQkyvvnys1IIb6k/JTKjMTijPii0pzU4kOMMhwcShK8W68B5QSLUtNTK9Iyc4ARApOW4OBRE uGdfAkozVtckJhbnJkOkTrFqMvRcfPuHyYhlrz8vFQpcd4jIDMEQIoySvPgRsCi9RKjrJQwLy MDA4MQT0FqUW5mCar8K0ZxDkYlYd5vIFN4MvNK4Da9AjqCCegIxuIbIEeUJCKkpBoY9VIsMze fYYp6rWZ6vIthqU1KSEPkyUDVAzyKfUrVa3Pyu3Lemd6a9SLqU1qJuWii3dcln8qqV8+89fLS h+PCTv/POS2tELiu63xqmvxpBusNy42Ob9aY7Pll3a+5lS8mX++p4T65cqema9Lv+XPXxS2oe eXbdfuMs8DU7c5vo2ZYFK+c/19uqxJLcUaioRZzUXEiABQM0eTRAgAA X-Env-Sender: yi.y.sun@linux.intel.com X-Msg-Ref: server-11.tower-206.messagelabs.com!1507448706!86188759!1 X-Originating-IP: [134.134.136.100] X-SpamReason: No, hits=0.0 required=7.0 tests= X-StarScan-Received: X-StarScan-Version: 9.4.45; banners=-,-,- X-VirusChecked: Checked Received: (qmail 27946 invoked from network); 8 Oct 2017 07:45:07 -0000 Received: from mga07.intel.com (HELO mga07.intel.com) (134.134.136.100) by server-11.tower-206.messagelabs.com with DHE-RSA-AES256-GCM-SHA384 encrypted SMTP; 8 Oct 2017 07:45:07 -0000 Received: from orsmga003.jf.intel.com ([10.7.209.27]) by orsmga105.jf.intel.com with ESMTP; 08 Oct 2017 00:45:04 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos; i="5.42,493,1500966000"; d="scan'208"; a="1022874813" Received: from vmmmba-s2600wft.bj.intel.com ([10.240.193.75]) by orsmga003.jf.intel.com with ESMTP; 08 Oct 2017 00:44:20 -0700 From: Yi Sun To: xen-devel@lists.xenproject.org Date: Sun, 8 Oct 2017 15:23:46 +0800 Message-Id: <1507447441-5422-2-git-send-email-yi.y.sun@linux.intel.com> X-Mailer: git-send-email 1.9.1 In-Reply-To: <1507447441-5422-1-git-send-email-yi.y.sun@linux.intel.com> References: <1507447441-5422-1-git-send-email-yi.y.sun@linux.intel.com> MIME-Version: 1.0 Cc: Yi Sun , Konrad Rzeszutek Wilk , Andrew Cooper , Ian Jackson , Julien Grall , Jan Beulich , Chao Peng , Wei Liu , Daniel De Graaf , =?UTF-8?q?Roger=20Pau=20Monn=C3=A9?= Subject: [Xen-devel] [PATCH v6 01/16] docs: create Memory Bandwidth Allocation (MBA) feature document X-BeenThere: xen-devel@lists.xen.org X-Mailman-Version: 2.1.18 Precedence: list List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Errors-To: xen-devel-bounces@lists.xen.org Sender: "Xen-devel" X-Virus-Scanned: ClamAV using ClamSMTP This patch creates MBA feature document in doc/features/. It describes key points to implement MBA which is described in details in Intel SDM "Introduction to Memory Bandwidth Allocation". Signed-off-by: Yi Sun Reviewed-by: Roger Pau Monné --- CC: Jan Beulich CC: Andrew Cooper CC: Wei Liu CC: Ian Jackson CC: Daniel De Graaf CC: Roger Pau Monné CC: Konrad Rzeszutek Wilk CC: Chao Peng CC: Julien Grall v6: - fix some words. (suggested by Roger Pau Monné) v5: - correct some words. (suggested by Roger Pau Monné) - change 'xl psr-mba-set 1 0xa' to 'xl psr-mba-set 1 10'. (suggested by Roger Pau Monné) v4: - add 'domain-name' as parameter of 'psr-mba-show/psr-mba-set'. (suggested by Roger Pau Monné) - fix some wordings. (suggested by Roger Pau Monné) - explain how user can know the MBA_MAX. (suggested by Roger Pau Monné) - move the description of 'Linear mode/Non-linear mode' into section of 'psr-mba-show'. (suggested by Roger Pau Monné) - change 'per-thread' to 'per-hyper-thread' to make it clearer. (suggested by Roger Pau Monné) - upgrade revision number. v3: - remove 'closed-loop' related description. (suggested by Roger Pau Monné) - explain 'linear' and 'non-linear' before mentioning them. (suggested by Roger Pau Monné) - adjust desription of 'psr-mba-set'. (suggested by Roger Pau Monné) - explain 'MBA_MAX'. (suggested by Roger Pau Monné) - remove 'n<64'. (suggested by Roger Pau Monné) - fix some wordings. (suggested by Roger Pau Monné) - add context in 'Testing' part to make things more clear. (suggested by Roger Pau Monné) v2: - declare 'HW' in Terminology. (suggested by Chao Peng) - replace 'COS ID of VCPU' to 'COS ID of domain'. (suggested by Chao Peng) - replace 'COS register' to 'Thrtl MSR'. (suggested by Chao Peng) - add description for 'psr-mba-show' to state that the decimal value is shown for linear mode but hexadecimal value is shown for non-linear mode. (suggested by Chao Peng) - remove content in 'Areas for improvement'. (suggested by Chao Peng) - use '<>' to specify mandatory argument to a command. (suggested by Wei Liu) v1: - remove a special character to avoid the error when building pandoc. --- docs/features/intel_psr_mba.pandoc | 297 +++++++++++++++++++++++++++++++++++++ 1 file changed, 297 insertions(+) create mode 100644 docs/features/intel_psr_mba.pandoc diff --git a/docs/features/intel_psr_mba.pandoc b/docs/features/intel_psr_mba.pandoc new file mode 100644 index 0000000..86df661 --- /dev/null +++ b/docs/features/intel_psr_mba.pandoc @@ -0,0 +1,297 @@ +% Intel Memory Bandwidth Allocation (MBA) Feature +% Revision 1.8 + +\clearpage + +# Basics + +---------------- ---------------------------------------------------- + Status: **Tech Preview** + +Architecture(s): Intel x86 + + Component(s): Hypervisor, toolstack + + Hardware: MBA is supported on Skylake Server and beyond +---------------- ---------------------------------------------------- + +# Terminology + +* CAT Cache Allocation Technology +* CBM Capacity BitMasks +* CDP Code and Data Prioritization +* COS/CLOS Class of Service +* HW Hardware +* MBA Memory Bandwidth Allocation +* MSRs Machine Specific Registers +* PSR Intel Platform Shared Resource +* THRTL Throttle value or delay value + +# Overview + +The Memory Bandwidth Allocation (MBA) feature provides indirect and approximate +control over memory bandwidth available per-core. This feature provides OS/ +hypervisor the ability to slow misbehaving apps/domains by using a credit-based +throttling mechanism. + +# User details + +* Feature Enabling: + + Add "psr=mba" to boot line parameter to enable MBA feature. + +* xl interfaces: + + 1. `psr-mba-show [domain-id|domain-name]`: + + Show memory bandwidth throttling for domain. Under different modes, it + shows different type of data. + + There are two modes: + Linear mode: the input precision is defined as 100-(MBA_MAX). For instance, + if the MBA_MAX value is 90, the input precision is 10%. Values not an even + multiple of the precision (e.g., 12%) will be rounded down (e.g., to 10% + delay applied) by HW automatically. The response of throttling value is + linear. + + Non-linear mode: input delay values are powers-of-two from zero to the + MBA_MAX value from CPUID. In this case any values not a power of two will + be rounded down the next nearest power of two by HW automatically. The + response of throttling value is non-linear. + + For linear mode, it shows the decimal value. For non-linear mode, it shows + hexadecimal value. + + 2. `psr-mba-set [OPTIONS] `: + + Set memory bandwidth throttling for domain. + + Options: + '-s': Specify the socket to process, otherwise all sockets are processed. + + Throttling value set in register implies the approximate amount of delaying + the traffic between core and memory. Higher throttling value result in + lower bandwidth. The max throttling value (MBA_MAX) supported can be + obtained through CPUID inside hypervisor. Users can fetch the MBA_MAX value + using the `psr-hwinfo` xl command. + +# Technical details + +MBA is a member of Intel PSR features, it shares the base PSR infrastructure +in Xen. + +## Hardware perspective + + MBA defines a range of MSRs to support specifying a delay value (Thrtl) per + COS, with details below. + + ``` + +----------------------------+----------------+ + | MSR (per socket) | Address | + +----------------------------+----------------+ + | IA32_L2_QOS_Ext_BW_Thrtl_0 | 0xD50 | + +----------------------------+----------------+ + | ... | ... | + +----------------------------+----------------+ + | IA32_L2_QOS_Ext_BW_Thrtl_n | 0xD50+n | + +----------------------------+----------------+ + ``` + + When context switch happens, the COS ID of domain is written to per-hyper- + thread MSR `IA32_PQR_ASSOC`, and then hardware enforces bandwidth allocation + according to the throttling value stored in the Thrtl MSR register. + +## The relationship between MBA and CAT/CDP + + Generally speaking, MBA is completely independent of CAT/CDP, and any + combination may be applied at any time, e.g. enabling MBA with CAT + disabled. + + But it needs to be noticed that MBA shares COS infrastructure with CAT, + although MBA is enumerated by different CPUID leaf from CAT (which + indicates that the max COS of MBA may be different from CAT). In some + cases, a domain is permitted to have a COS that is beyond one (or more) + of PSR features but within the others. For instance, let's assume the max + COS of MBA is 8 but the max COS of L3 CAT is 16, when a domain is assigned + 9 as COS, the L3 CAT CBM associated to COS 9 would be enforced, but for MBA, + the HW works as default value is set since COS 9 is beyond the max COS (8) + of MBA. + +## Design Overview + +* Core COS/Thrtl association + + When enforcing Memory Bandwidth Allocation, all cores of domains have + the same default Thrtl MSR (COS0) which stores the same Thrtl (0). The + default Thrtl MSR is used only in hypervisor and is transparent to tool stack + and user. + + System administrators can change PSR allocation policy at runtime by + using the tool stack. Since MBA shares COS ID with CAT/CDP, a COS ID + corresponds to a 2-tuple, like [CBM, Thrtl] with only-CAT enabled, when CDP + is enabled, the COS ID corresponds to a 3-tuple, like [Code_CBM, Data_CBM, + Thrtl]. If neither CAT nor CDP is enabled, things are easier, since one COS + ID corresponds to one Thrtl. + +* VCPU schedule + + This part reuses CAT COS infrastructure. + +* Multi-sockets + + Different sockets may have different MBA capabilities (like max COS) + although it is consistent on the same socket. So the capability + of per-socket MBA is specified. + + This part reuses CAT COS infrastructure. + +## Implementation Description + +* Hypervisor interfaces: + + 1. Boot line param: "psr=mba" to enable the feature. + + 2. SYSCTL: + - XEN_SYSCTL_PSR_MBA_get_info: Get system MBA information. + + 3. DOMCTL: + - XEN_DOMCTL_PSR_MBA_OP_GET_THRTL: Get throttling for a domain. + - XEN_DOMCTL_PSR_MBA_OP_SET_THRTL: Set throttling for a domain. + +* xl interfaces: + + 1. psr-mba-show [domain-id] + Show system/domain runtime MBA throttling value. For linear mode, + it shows the decimal value. For non-linear mode, it shows hexadecimal + value. + => XEN_SYSCTL_PSR_MBA_get_info/XEN_DOMCTL_PSR_MBA_OP_GET_THRTL + + 2. psr-mba-set [OPTIONS] + Set bandwidth throttling for a domain. + => XEN_DOMCTL_PSR_MBA_OP_SET_THRTL + + 3. psr-hwinfo + Show PSR HW information, including L3 CAT/CDP/L2 CAT/MBA. + => XEN_SYSCTL_PSR_MBA_get_info + +* Key data structure: + + 1. Feature HW info + + ``` + struct { + unsigned int thrtl_max; + bool linear; + } mba; + + - Member `thrtl_max` + + `thrtl_max` is the max throttling value to be set, i.e. MBA_MAX. + + - Member `linear` + + `linear` means the response of delay value is linear or not. + + As mentioned above, MBA is a member of Intel PSR features, it shares the + base PSR infrastructure in Xen. For example, the 'cos_max' is a common HW + property for all features. So, for other data structure details, please + refer to 'intel_psr_cat_cdp.pandoc'. + +# Limitations + +MBA can only work on HW which supports it (check CPUID). + +# Testing + +We can execute these commands to verify MBA on different HWs supporting them. + +For example: + 1. User can get the MBA hardware info through 'psr-hwinfo' command. From + result, user can know if this hardware works under linear mode or non- + linear mode, the max throttling value (MBA_MAX) and so on. + + root@:~$ xl psr-hwinfo --mba + Memory Bandwidth Allocation (MBA): + Socket ID : 0 + Linear Mode : Enabled + Maximum COS : 7 + Maximum Throttling Value: 90 + Default Throttling Value: 0 + + 2. Then, user can set a throttling value to a domain. For example, set '10', + i.e 10% delay. + + root@:~$ xl psr-mba-set 1 10 + + 3. User can check the current configuration of the domain through + 'psr-mab-show'. For linear mode, the decimal value is shown. + + root@:~$ xl psr-mba-show 1 + Socket ID : 0 + Default THRTL : 0 + ID NAME THRTL + 1 ubuntu14 10 + +# Areas for improvement + +N/A + +# Known issues + +N/A + +# References + +"INTEL RESOURCE DIRECTOR TECHNOLOGY (INTEL RDT) ALLOCATION FEATURES" [Intel 64 and IA-32 Architectures Software Developer Manuals, vol3](http://www.intel.com/content/www/us/en/processors/architectures-software-developer-manuals.html) + +# History + +------------------------------------------------------------------------ +Date Revision Version Notes +---------- -------- -------- ------------------------------------------- +2017-01-10 1.0 Xen 4.9 Design document written +2017-07-10 1.1 Xen 4.10 Changes: + 1. Modify data structure according to latest + codes; + 2. Add content for 'Areas for improvement'; + 3. Other minor changes. +2017-08-09 1.2 Xen 4.10 Changes: + 1. Remove a special character to avoid error when + building pandoc. +2017-08-15 1.3 Xen 4.10 Changes: + 1. Add terminology 'HW'. + 2. Change 'COS ID of VCPU' to 'COS ID of domain'. + 3. Change 'COS register' to 'Thrtl MSR'. + 4. Explain the value shown for 'psr-mba-show' under + different modes. + 5. Remove content in 'Areas for improvement'. +2017-08-16 1.4 Xen 4.10 Changes: + 1. Add '<>' for mandatory argument. +2017-08-30 1.5 Xen 4.10 Changes: + 1. Modify words in 'Overview' to make it easier to + understand. + 2. Explain 'linear/non-linear' modes before mention + them. + 3. Explain throttling value more accurate. + 4. Explain 'MBA_MAX'. + 5. Correct some words in 'Design Overview'. + 6. Change 'mba_info' to 'mba' according to code + changes. Also, modify contents of it. + 7. Add context in 'Testing' part to make things + more clear. + 8. Remove 'n<64' to avoid out-of-sync. +2017-09-21 1.6 Xen 4.10 Changes: + 1. Add 'domain-name' as parameter of 'psr-mba-show/ + psr-mba-set'. + 2. Fix some wordings. + 3. Explain how user can know the MBA_MAX. + 4. Move the description of 'Linear mode/Non-linear + mode' into section of 'psr-mba-show'. + 5. Change 'per-thread' to 'per-hyper-thread'. +2017-09-29 1.7 Xen 4.10 Changes: + 1. Correct some words. + 2. Change 'xl psr-mba-set 1 0xa' to + 'xl psr-mba-set 1 10' +2017-10-08 1.8 Xen 4.10 Changes: + 1. Correct some words. +---------- -------- -------- -------------------------------------------