.. SPDX-License-Identifier: GPL-2.0
.. include:: <isonum.txt>
===========================================
User Interface for Resource Control feature
===========================================
:Copyright: |copy| 2016 Intel Corporation
:Authors: - Fenghua Yu <fenghua.yu@intel.com>
- Tony Luck <tony.luck@intel.com>
- Vikas Shivappa <vikas.shivappa@intel.com>
Intel refers to this feature as Intel Resource Director Technology(Intel(R) RDT).
AMD refers to this feature as AMD Platform Quality of Service(AMD QoS).
This feature is enabled by the CONFIG_X86_CPU_RESCTRL and the x86 /proc/cpuinfo
flag bits:
=============================================== ================================
RDT (Resource Director Technology) Allocation "rdt_a"
CAT (Cache Allocation Technology) "cat_l3", "cat_l2"
CDP (Code and Data Prioritization) "cdp_l3", "cdp_l2"
CQM (Cache QoS Monitoring) "cqm_llc", "cqm_occup_llc"
MBM (Memory Bandwidth Monitoring) "cqm_mbm_total", "cqm_mbm_local"
MBA (Memory Bandwidth Allocation) "mba"
SMBA (Slow Memory Bandwidth Allocation) ""
BMEC (Bandwidth Monitoring Event Configuration) ""
=============================================== ================================
Historically, new features were made visible by default in /proc/cpuinfo. This
resulted in the feature flags becoming hard to parse by humans. Adding a new
flag to /proc/cpuinfo should be avoided if user space can obtain information
about the feature from resctrl's info directory.
To use the feature mount the file system::
# mount -t resctrl resctrl [-o cdp[,cdpl2][,mba_MBps][,debug]] /sys/fs/resctrl
mount options are:
"cdp":
Enable code/data prioritization in L3 cache allocations.
"cdpl2":
Enable code/data prioritization in L2 cache allocations.
"mba_MBps":
Enable the MBA Software Controller(mba_sc) to specify MBA
bandwidth in MiBps
"debug":
Make debug files accessible. Available debug files are annotated with
"Available only with debug option".
L2 and L3 CDP are controlled separately.
RDT features are orthogonal. A particular system may support only
monitoring, only control, or both monitoring and control. Cache
pseudo-locking is a unique way of using cache control to "pin" or
"lock" data in the cache. Details can be found in
"Cache Pseudo-Locking".
The mount succeeds if either of allocation or monitoring is present, but
only those files and directories supported by the system will be created.
For more details on the behavior of the interface during monitoring
and allocation, see the "Resource alloc and monitor groups" section.
Info directory
==============
The 'info' directory contains information about the enabled
resources. Each resource has its own subdirectory. The subdirectory
names reflect the resource names.
Each subdirectory contains the following files with respect to
allocation:
Cache resource(L3/L2) subdirectory contains the following files
related to allocation:
"num_closids":
The number of CLOSIDs which are valid for this
resource. The kernel uses the smallest number of
CLOSIDs of all enabled resources as limit.
"cbm_mask":
The bitmask which is valid for this resource.
This mask is equivalent to 100%.
"min_cbm_bits":
The minimum number of consecutive bits which
must be set when writing a mask.
"shareable_bits":
Bitmask of shareable resource with other 