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README for Intel(R) RDT Software Package

Coverity Status License

Contents

  • Overview
  • Package Content
  • Hardware Support
  • OS Support
  • Software Compatibility
  • Legal Disclaimer

Overview

This software package provides basic support for Intel(R) Resource Director Technology (Intel(R) RDT) and Intel(R) I/O Resource Director Technology (Intel(R) I/O RDT) including: Cache Monitoring Technology (CMT), Memory Bandwidth Monitoring (MBM), Cache Allocation Technology (CAT), Code and Data Prioritization (CDP) and Memory Bandwidth Allocation (MBA).

In principle, the software programs the technologies via Model Specific Registers (MSR) on a hardware thread basis. MSR access is arranged via a standard operating system driver: msr on Linux and cpuctl on FreeBSD. In the most common architectural implementations, presence of the technologies is detected via the CPUID instruction.

In a limited number of special cases where CAT is not architecturally supported on a particular SKU (but instead a non-architectural (model-specific) implementation exists) it can be detected via brand string. This brand string is read from CPUID and compared to a table of known-supported SKUs. If needed, a final check is to probe the specific MSR’s to discover hardware capabilities, however it is recommended that CPUID enumeration should be used wherever possible.

From software version v1.0.0 the library adds option to use Intel(R) RDT via available OS interfaces (perf and resctrl on Linux). The library detects presence of these interfaces and allows to select the preferred one through a configuration option. As the result, existing tools like 'pqos' or 'rdtset' can also be used to manage Intel(R) RDT in an OS compatible way. As of release v4.3.0, OS interface became the default option. 'pqos' tool wrappers have been added to help with the interface selection. 'pqos-os' and 'pqos-msr' for OS and MSR interface operations respectively.

PID API compile time option has been removed and the APIs are always available. Note that proper operation of these APIs depends on availability and selection of OS interface.

This software package is maintained, updated and developed on https://github.com/intel/intel-cmt-cat

https://github.com/intel/intel-cmt-cat/wiki provides FAQ, usage examples and useful links.

Please refer to INSTALL file for package installation instructions.

Package Content

"lib" directory:
Includes software library files providing API's for technology detection, monitoring and allocation. Please refer to the library README for more details (lib/README).

“lib/perl” directory:
Includes PQoS library Perl wrapper. Please refer to the interface README for more details (lib/perl/README).

“lib/python” directory:
Includes PQoS library Python 3.x wrapper. Please refer to the interface README for more details (lib/python/README.md).

"pqos" directory:
Includes source files for a utility that provides command line access to Intel(R) RDT. The utility links against the library and programs the technologies via its API's. Please refer to the utility README for more details "pqos/README". Manual page of "pqos" utility also provides information about tool usage: $ man pqos

"rdtset" directory:
Includes source files for a utility that provides "taskset"-like functionality for RDT configuration. The utility links against the library and programs the technologies via its API's. Please refer to the utility README for more details "rdtset/README". Manual page of "rdtset" utility also provides information about tool usage: $ man rdtset

"appqos" directory:
Includes source files for an application that allows to group apps into priority based pools. Each pool is assigned an Intel(R) RDT and Intel(R) SST configuration that can be set on startup or at runtime through a REST API. Please refer to the application README for more details "appqos/README".

"appqos_client" directory:
Includes source files for an App QoS client web application. The app provides a simple user interface to remotely configure Intel(R) RDT and Intel(R) SST on systems where App QoS is running. Please refer to the application README for more details "appqos_client/README".

"examples" directory:
Includes C and Perl examples of Intel(R) RDT usage via the library API's. Please refer to README file for more details "examples/README".

"snmp" directory:
Includes Net-SNMP AgentX subagent written in Perl to demonstrate the use of the PQoS library Perl wrapper API. Please refer to README file for more details "snmp/README".

"tools" directory:
Includes membw tool for stressing memory bandwidth with different operations.

"srpm" directory:
Includes *.src *.rpm and *.spec files for the software package.

"ChangeLog" file:
Brief description of changes between releases.

"INSTALL" file:
Installation instructions.

"LICENSE" file:
License of the package.

"unit-test" directory:
Unit tests

Hardware Support

Supported products can be found in Addendum A of the Intel® Resource Director Technology (Intel® RDT) Architecture Specification: https://www.intel.com/content/www/us/en/content-details/789566/intel-resource-director-technology-intel-rdt-architecture-specification.html

Addendum B contains a list of processors with model-specific Intel® RDT Features.
Note: Detection of model-specific features requires the RDT_PROBE_MSR environment variable to be set when using the library and utilities. These features are only available when using the MSR interface. See the "Interfaces" section below for more information. See the wiki for usage examples.

For additional Intel(R) RDT details please refer to the Intel(R) Architecture Software Development Manuals available at: https://www.intel.com/content/www/us/en/develop/download/intel-64-and-ia-32-architectures-sdm-combined-volumes-1-2a-2b-2c-2d-3a-3b-3c-3d-and-4.html Specific information can be found in volume 3a, Chapters 17.18 and 17.19.

OS Support

Overview

Linux is the primary supported operating system at the moment. There is a FreeBSD port of the software but due to limited validation scope it is rather experimental at this stage. Although most modern Linux kernels include support for Intel(R) RDT, the Intel(R) RDT software package predates these extensions and can operate with and without kernel support. The Intel(R) RDT software can detect and leverage these kernel extensions when available to add functionality, but is also compatible with legacy kernels.

OS Frameworks

Linux kernel support for Intel(R) RDT was originally introduced with Linux perf system call extensions for CMT and MBM. More recently, the Resctrl interface added support for CAT, CDP and MBA. On modern Linux kernels, it is advised to use the kernel/OS interface when available. Details about these interfaces can be found in resctrl_ui.txt. This software package, Intel(R) RDT, remains to work seamlessly in all Linux kernel versions.

Interfaces

The Intel(R) RDT software library and utilities offer two interfaces to program Intel(R) RDT technologies, these are the MSR & OS interfaces.

The MSR interface is used to configure the platform by programming the hardware (MSR's) directly. This is the legacy interface and requires no kernel support for Intel(R) RDT but is limited to monitoring and managing resources on a per core basis.

The OS interface was later added to the package and when selected, the library will leverage Linux kernel extensions to program these technologies. This allows monitoring and managing resources on a per core/process basis and should be used when available.

Please see the tables below for more information on when Intel(R) RDT feature (MSR & OS) support was added to the package.

Table 2. MSR interface feature support
Intel(R) RDT version RDT feature enabled Kernel version required
0.1.3 L3 CAT, CMT, MBM Any
0.1.4 L3 CDP Any
0.1.5 L2 CAT Any
1.2.0 MBA Any
2.0.0 L2 CDP Any
5.0.0 I/O RDT Any
Table 3. OS interface feature support
Intel(R) RDT version RDT feature enabled Kernel version required Recommended interface
0.1.4 CMT (Perf) 4.1 MSR (1)
1.0.0 MBM (Perf) 4.7 MSR (1)
1.1.0 L3 CAT, L3 CDP, L2 CAT (Resctrl) 4.10 OS for allocation only (with the exception of MBA) MSR for allocation + monitoring (2)
1.2.0 MBA (Resctrl) 4.12 OS for allocation only MSR for allocation + monitoring (2)
2.0.0 CMT, MBM (Resctrl) 4.14 OS
2.0.0 L2 CDP 4.16 OS
3.0.0 MBA CTRL (Resctrl) 4.18 OS

References:

  1. Monitoring with Perf on a per core basis is not supported and returns invalid results.
  2. The MSR and OS interfaces are not compatible. MSR interface is recommended if monitoring and allocation is to be used.

Software dependencies

The only dependencies of Intel(R) RDT is access to C and pthreads libraries and:

  • without kernel extensions - 'msr' kernel module
  • with kernel extensions - Intel(R) RDT extended Perf system call and Resctrl filesystem

Enable Intel(R) RDT support in:

  • kernel v4.10 - v4.13 with kernel configuration option CONFIG_INTEL_RDT_A
  • kernel v4.14+ with kernel configuration option CONFIG_INTEL_RDT
  • kernel v5.0+ with kernel configuration option CONFIG_X86_RESCTRL

Note: No kernel configuration options required before v4.10.

Software Compatibility

In short, using Intel(R) RDT or PCM software together with Linux perf and cgroup frameworks is not allowed at the moment.

As disappointing as it is, use of Linux perf for CMT & MBM and Intel(R) RDT for CAT & CDP is not allowed. This is because Linux perf overrides existing CAT configuration during its operations.

There are a number of options to choose from in order to make use of CAT:

  • Intel(R) RDT software for CMT/MBM/CAT and CDP (core granularity only)
  • use Linux resctrl for CAT and Linux perf for monitoring (kernel 4.10+)
  • patch kernel with an out of tree cgroup patch (CAT) and only use perf for monitoring (CMT kernels 4.1+, MBM kernels 4.6+)

Table 4. Software interoperability matrix

Intel(R) RDT PCM Linux perf Linux cgroup Linux resctrl
Intel(R) RDT Yes(1) Yes(2) Yes(5) No Yes(5)
PCM Yes(2) Yes No No No
Linux perf Yes(5) No Yes Yes(3) Yes
Linux cgroup No No Yes Yes(3) No
Linux resctrl (4) Yes(5) No Yes No Yes

References:

  1. pqos monitoring from Intel(R) RDT can detect other pqos monitoring processes in the system. rdtset from Intel(R) RDT detects other processes started with rdtset and it will not use their CAT/CDP resources.

  2. pqos from Intel(R) RDT can detect that PCM monitors cores and it will not attempt to hijack the cores unless forced. However, if pqos monitoring is started first and then PCM is started then the latter one will hijack monitoring infrastructure from pqos for its use.

  3. Linux cgroup kernel patch https://www.kernel.org/doc/Documentation/cgroup-v1/cgroups.txt

  4. Linux kernel version 4.10 and newer. A wiki for Intel resctrl is available at: https://github.com/intel/intel-cmt-cat/wiki/resctrl

  5. Only with Linux kernel version 4.10 (and newer), Intel(R) RDT version 1.0.0 (and newer) with selected OS interface See '-I' option in 'man pqos' or 'pqos-os'.

PCM is available at: https://github.com/opcm/pcm

Table 5. Intel(R) RDT software enabling status.

Core Task CMT MBM L3 CAT L3 CDP L2 CAT MBA
Intel(R) RDT Yes Yes(7) Yes Yes Yes Yes Yes Yes
Linux perf Yes(6) Yes Yes(1) Yes(2) No(3) No(3) No(3) No
Linux cgroup No Yes No No Yes(4) No No No
Linux resctrl (5) Yes Yes Yes(8) Yes(8) Yes Yes Yes Yes(9)

Legend:

  • Core - use of technology with core granularity
  • Task - use of technology per task or group of tasks

References:

  1. Linux kernel version 4.1 and newer
  2. Linux kernel version 4.6 and newer
  3. Linux perf corrupts CAT and CDP configuration even though it doesn't enable it
  4. This is patch and relies on Linux perf enabling
  5. Linux kernel version 4.10 and newer
  6. perf API allows for CMT/MBM core monitoring but returned values are incorrect
  7. Intel(R) RDT version 1.0.0 monitoring only and depends on kernel support
  8. Linux kernel version 4.14 and newer
  9. Linux kernel version 4.12 and newer

Legal Disclaimer

THIS SOFTWARE IS PROVIDED BY INTEL"AS IS". NO LICENSE, EXPRESS OR IMPLIED, BY ESTOPPEL OR OTHERWISE, TO ANY INTELLECTUAL PROPERTY RIGHTS ARE GRANTED THROUGH USE. EXCEPT AS PROVIDED IN INTEL'S TERMS AND CONDITIONS OF SALE, INTEL ASSUMES NO LIABILITY WHATSOEVER AND INTEL DISCLAIMS ANY EXPRESS OR IMPLIED WARRANTY, RELATING TO SALE AND/OR USE OF INTEL PRODUCTS INCLUDING LIABILITY OR WARRANTIES RELATING TO FITNESS FOR A PARTICULAR PURPOSE, MERCHANTABILITY, OR INFRINGEMENT OF ANY PATENT, COPYRIGHT OR OTHER INTELLECTUAL PROPERTY RIGHT.