From patchwork Tue Sep 5 09:32:23 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Yi Sun X-Patchwork-Id: 9938323 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 91753601EB for ; Tue, 5 Sep 2017 09:53:27 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 8277328902 for ; Tue, 5 Sep 2017 09:53:27 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 7585C2890B; Tue, 5 Sep 2017 09:53:27 +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 9205C28902 for ; Tue, 5 Sep 2017 09:53:26 +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 1dpAVY-0006u2-Gp; Tue, 05 Sep 2017 09:51:00 +0000 Received: from mail6.bemta6.messagelabs.com ([193.109.254.103]) by lists.xenproject.org with esmtp (Exim 4.84_2) (envelope-from ) id 1dpAVW-0006sx-9J for xen-devel@lists.xenproject.org; Tue, 05 Sep 2017 09:50:58 +0000 Received: from [85.158.143.35] by server-3.bemta-6.messagelabs.com id 8D/64-03093-1837EA95; Tue, 05 Sep 2017 09:50:57 +0000 X-Brightmail-Tracker: H4sIAAAAAAAAA+NgFtrMIsWRWlGSWpSXmKPExsXS1tYhottQvC7 S4Mt5CYvvWyYzOTB6HP5whSWAMYo1My8pvyKBNaP92FnGgo8JFTumvWNtYFzn3sXIxSEkMJ1R 4tSkKaxdjJwcEgK8EkeWzYCy/SVOTlzBBGILCTQwSkw/LwViswmoSzz+2gMWFxFQkri3ajITy CBmgXNMEns+7gBLCAtESjz//5ENxGYRUJU4MW8vYxcjBwevgLvEvXkBEPPlJE4em8wKEuYU8J BYeq0OYpW7xJ9td8FO4BUQlDg58wkLSAkz0Nr184RAwswC8hLNW2czT2AUmIWkahZC1SwkVQs YmVcxahSnFpWlFukaGuolFWWmZ5TkJmbm6BoamOnlphYXJ6an5iQmFesl5+duYgQGJgMQ7GD8 tCzgEKMkB5OSKG9o4rpIIb6k/JTKjMTijPii0pzU4kOMMhwcShK8t4qAcoJFqempFWmZOcAYg UlLcPAoifCeA0nzFhck5hZnpkOkTjEqSonzHgdJCIAkMkrz4NpgcXmJUVZKmJcR6BAhnoLUot zMElT5V4ziHIxKwrxLQKbwZOaVwE1/BbSYCWhx1cs1IItLEhFSUg2MEVmnv8cJFhw6L3pvYbB GwJGO+fvzV+m6lD2/cYO/LHJbkvvR1RpPPqlURpWI9EpOM5km9nNbV8AZx4s/dqmxzdLezjH3 0OL7jNu9X//aen1r/a5N56Q/GN2b/dYvLb9o+dkfZlMC3olNKH77PYrt5S3Ni3k7laew+Xbbt 7fwd9trut/cHOJ9WImlOCPRUIu5qDgRALWy5kzGAgAA X-Env-Sender: yi.y.sun@linux.intel.com X-Msg-Ref: server-7.tower-21.messagelabs.com!1504605051!81282253!2 X-Originating-IP: [134.134.136.20] X-SpamReason: No, hits=0.0 required=7.0 tests=sa_preprocessor: VHJ1c3RlZCBJUDogMTM0LjEzNC4xMzYuMjAgPT4gMzU1MzU4\n X-StarScan-Received: X-StarScan-Version: 9.4.45; banners=-,-,- X-VirusChecked: Checked Received: (qmail 1305 invoked from network); 5 Sep 2017 09:50:55 -0000 Received: from mga02.intel.com (HELO mga02.intel.com) (134.134.136.20) by server-7.tower-21.messagelabs.com with DHE-RSA-AES256-GCM-SHA384 encrypted SMTP; 5 Sep 2017 09:50:55 -0000 Received: from fmsmga003.fm.intel.com ([10.253.24.29]) by orsmga101.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 05 Sep 2017 02:50:55 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.41,479,1498546800"; d="scan'208";a="897185109" Received: from vmmmba-s2600wft.bj.intel.com ([10.240.193.80]) by FMSMGA003.fm.intel.com with ESMTP; 05 Sep 2017 02:50:50 -0700 From: Yi Sun To: xen-devel@lists.xenproject.org Date: Tue, 5 Sep 2017 17:32:23 +0800 Message-Id: <1504603957-5389-2-git-send-email-yi.y.sun@linux.intel.com> X-Mailer: git-send-email 1.9.1 In-Reply-To: <1504603957-5389-1-git-send-email-yi.y.sun@linux.intel.com> References: <1504603957-5389-1-git-send-email-yi.y.sun@linux.intel.com> MIME-Version: 1.0 Cc: kevin.tian@intel.com, wei.liu2@citrix.com, andrew.cooper3@citrix.com, dario.faggioli@citrix.com, ian.jackson@eu.citrix.com, Yi Sun , julien.grall@arm.com, mengxu@cis.upenn.edu, jbeulich@suse.com, chao.p.peng@linux.intel.com, dgdegra@tycho.nsa.gov, roger.pau@citrix.com Subject: [Xen-devel] [PATCH v3 01/15] 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 --- 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 | 283 +++++++++++++++++++++++++++++++++++++ 1 file changed, 283 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..693ef45 --- /dev/null +++ b/docs/features/intel_psr_mba.pandoc @@ -0,0 +1,283 @@ +% Intel Memory Bandwidth Allocation (MBA) Feature +% Revision 1.5 + +\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]`: + + Show memory bandwidth throttling for domain. Under different modes, it + shows different type of data. + + There are two modes: + Linear mode: the response of throttling value is linear. + Non-linear mode: 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. The higher throttling value results in + lower bandwidth. The max throttling value (MBA_MAX) supported can be got + through CPUID. + + 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. + + 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. + +# 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-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 ability (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 would + share 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 'intel_psr_cat_cdp.pandoc'. + +# Limitations + +MBA can only work on HW which enables it (check by 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 '0xa', + i.e 10% delay. + + root@:~$ xl psr-mba-set 1 0xa + + 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. +---------- -------- -------- -------------------------------------------