linux/Documentation/admin-guide/pm, branch v6.7

intel_idle: Add ibrs_off module parameter to force-disable IBRS

2023-10-07T09:33:28Z

Commit bf5835bcdb96 ("intel_idle: Disable IBRS during long idle") disables IBRS when the cstate is 6 or lower. However, there are some use cases where a customer may want to use max_cstate=1 to lower latency. Such use cases will suffer from the performance degradation caused by the enabling of IBRS in the sibling idle thread. Add a "ibrs_off" module parameter to force disable IBRS and the CPUIDLE_FLAG_IRQ_ENABLE flag if set. In the case of a Skylake server with max_cstate=1, this new ibrs_off option will likely increase the IRQ response latency as IRQ will now be disabled. When running SPECjbb2015 with cstates set to C1 on a Skylake system. First test when the kernel is booted with: "intel_idle.ibrs_off": max-jOPS = 117828, critical-jOPS = 66047 Then retest when the kernel is booted without the "intel_idle.ibrs_off" added: max-jOPS = 116408, critical-jOPS = 58958 That means booting with "intel_idle.ibrs_off" improves performance by: max-jOPS: +1.2%, which could be considered noise range. critical-jOPS: +12%, which is definitely a solid improvement. The admin-guide/pm/intel_idle.rst file is updated to add a description about the new "ibrs_off" module parameter. Signed-off-by: Waiman Long Signed-off-by: Ingo Molnar Acked-by: Rafael J. Wysocki Cc: Linus Torvalds Link: https://lore.kernel.org/r/20230727184600.26768-5-longman@redhat.com

platform/x86/intel-uncore-freq: Support for cluster level controls

2023-05-09T09:54:42Z

An SoC can contain multiple power domains with individual or collection of mesh partitions. This partition is called fabric cluster. Certain type of meshes will need to run at the same frequency, they will be placed in the same fabric cluster. Benefit of fabric cluster is that it offers a scalable mechanism to deal with partitioned fabrics in a SoC. The current sysfs interface supports control at package and die level. This interface is not enough to support more granular control at fabric cluster level. SoCs with the support of TPMI (Topology Aware Register and PM Capsule Interface), can have multiple power domains. Each power domain can contain one or more fabric clusters. To support such granular controls, enhance uncore common to optionally create new directories to provide controls at fabric cluster level. It is also important to have flexibility to change granularity for future version of SoCs. If the directory name contains scope like: "package_*_die_*_power_domain_*_cluster_*", then this is not expandable. The cpufreq policies also have different scopes. There the scope of the policy (affected_cpus) specified by attributes inside each policy. So, follow the same model for uncore frequency scaling sysfs as: "sys/devices/system/cpu/cpufreq/policy*" Allow client drivers to optionally support granular control for each fabric cluster. Here, the directory name will be "uncore" suffixed with an unique instance number. For example: uncore00, uncore01 etc. Attributes in the directory identify package id, power domain and fabric cluster id. This interface is expandable even if some new level of granularity is introduced. A new sysfs attribute can identify new level. For compatibility with the existing sysfs and provide easy way to set limits for each fabric cluster in the package/die, the existing control at package/die levels are still provided. For majority of users, this is an easy approach. For example: On a single package/die system, with three power domains and one fabric cluster per power domain: $tree -L 2 /sys/devices/system/cpu/intel_uncore_frequency/ /sys/devices/system/cpu/intel_uncore_frequency/ ├── package_00_die_00 │ ├── current_freq_khz │ ├── initial_max_freq_khz │ ├── initial_min_freq_khz │ ├── max_freq_khz │ └── min_freq_khz ├── uncore00 │ ├── current_freq_khz │ ├── domain_id │ ├── fabric_cluster_id │ ├── initial_max_freq_khz │ ├── initial_min_freq_khz │ ├── max_freq_khz │ ├── min_freq_khz │ └── package_id ├── uncore01 │ ├── current_freq_khz │ ├── domain_id │ ├── fabric_cluster_id │ ├── initial_max_freq_khz │ ├── initial_min_freq_khz │ ├── max_freq_khz │ ├── min_freq_khz │ └── package_id └── uncore02 ├── current_freq_khz ├── domain_id ├── fabric_cluster_id ├── initial_max_freq_khz ├── initial_min_freq_khz ├── max_freq_khz ├── min_freq_khz └── package_id The attribute for cluster id is "fabric_cluster_id" instead of just "cluster_id" is to avoid confusion with usage of term clusters in other part of the Linux kernel. Signed-off-by: Srinivas Pandruvada Reviewed-by: Zhang Rui Tested-by: Wendy Wang Link: https://lore.kernel.org/r/20230418171340.681662-3-srinivas.pandruvada@linux.intel.com Signed-off-by: Hans de Goede

Documentation: cpufreq: amd-pstate: Update amd_pstate status sysfs for guided

2023-03-17T18:06:23Z

Update amd_pstate status sysfs for guided mode. Acked-by: Huang Rui Reviewed-by: Bagas Sanjaya Reviewed-by: Mario Limonciello Tested-by: Oleksandr Natalenko Signed-off-by: Wyes Karny Signed-off-by: Rafael J. Wysocki

Merge tag 'docs-6.3' of git://git.lwn.net/linux

2023-02-22T20:00:20Z

Pull documentation updates from Jonathan Corbet: "It has been a moderately calm cycle for documentation; the significant changes include: - Some significant additions to the memory-management documentation - Some improvements to navigation in the HTML-rendered docs - More Spanish and Chinese translations ... and the usual set of typo fixes and such" * tag 'docs-6.3' of git://git.lwn.net/linux: (68 commits) Documentation/watchdog/hpwdt: Fix Format Documentation/watchdog/hpwdt: Fix Reference Documentation: core-api: padata: correct spelling docs/mm: Physical Memory: correct spelling in reference to CONFIG_PAGE_EXTENSION docs: Use HTML comments for the kernel-toc SPDX line docs: Add more information to the HTML sidebar Documentation: KVM: Update AMD memory encryption link printk: Document that CONFIG_BOOT_PRINTK_DELAY required for boot_delay= Documentation: userspace-api: correct spelling Documentation: sparc: correct spelling Documentation: driver-api: correct spelling Documentation: admin-guide: correct spelling docs: add workload-tracing document to admin-guide docs/admin-guide/mm: remove useless markup docs/mm: remove useless markup docs/mm: Physical Memory: remove useless markup docs/sp_SP: Add process magic-number translation docs: ftrace: always use canonical ftrace path Doc/damon: fix the data path error dma-buf: Add "dma-buf" to title of documentation ...

Documentation: amd-pstate: disambiguate user space sections

2023-02-15T14:58:16Z

kernel test robot reported htmldocs warning: Documentation/admin-guide/pm/amd-pstate.rst:343: WARNING: duplicate label admin-guide/pm/amd-pstate:user space interface in ``sysfs``, other instance in Documentation/admin-guide/pm/amd-pstate.rst The documentation contains two sections with the same "User Space Interface in ``sysfs``" title. The first one deals with per-policy sysfs and the second one is about general attributes (currently only global attributes are documented). Disambiguate title text of both sections to fix the warning. Link: https://lore.kernel.org/linux-doc/202302151041.0SWs1RHK-lkp@intel.com/ Fixes: b9e6a2d47b2565 ("Documentation: amd-pstate: introduce new global sysfs attributes") Reported-by: kernel test robot Signed-off-by: Bagas Sanjaya Reviewed-by: Wyes Karny Acked-by: Huang Rui Signed-off-by: Rafael J. Wysocki

Documentation: amd-pstate: introduce new global sysfs attributes

2023-02-03T20:59:42Z

The amd-pstate driver supports switching working modes at runtime. Users can view and change modes by interacting with the "status" sysfs attribute. 1) check driver mode: $ cat /sys/devices/system/cpu/amd-pstate/status 2) switch mode: `# echo "passive" | sudo tee /sys/devices/system/cpu/amd-pstate/status` or `# echo "active" | sudo tee /sys/devices/system/cpu/amd-pstate/status` Acked-by: Huang Rui Reviewed-by: Mario Limonciello Reviewed-by: Wyes Karny Tested-by: Wyes Karny Signed-off-by: Perry Yuan Signed-off-by: Rafael J. Wysocki

Documentation: amd-pstate: add amd pstate driver mode introduction

2023-02-03T20:59:42Z

The amd-pstate driver has two operation modes supported: * CPPC Autonomous (active) mode * CPPC non-autonomous (passive) mode. active mode and passive mode can be chosen by different kernel parameters. Acked-by: Huang Rui Reviewed-by: Mario Limonciello Reviewed-by: Wyes Karny Tested-by: Wyes Karny Signed-off-by: Perry Yuan Signed-off-by: Rafael J. Wysocki

Documentation: amd-pstate: add EPP profiles introduction

2023-02-03T20:59:41Z

The amd-pstate driver supports a feature called energy performance preference (EPP). Add information to the documentation to explain how users can interact with the sysfs files for this feature. 1) See all EPP profiles $ sudo cat /sys/devices/system/cpu/cpu0/cpufreq/energy_performance_available_preferences default performance balance_performance balance_power power 2) Check current EPP profile $ sudo cat /sys/devices/system/cpu/cpu0/cpufreq/energy_performance_preference performance 3) Set new EPP profile $ sudo bash -c "echo power > /sys/devices/system/cpu/cpu0/cpufreq/energy_performance_preference" Acked-by: Huang Rui Reviewed-by: Mario Limonciello Reviewed-by: Wyes Karny Tested-by: Wyes Karny Signed-off-by: Perry Yuan Signed-off-by: Rafael J. Wysocki

Documentation: admin-guide: correct spelling

2023-02-02T18:04:42Z

Correct spelling problems for Documentation/admin-guide/ as reported by codespell. Signed-off-by: Randy Dunlap Reviewed-by: Mukesh Ojha Cc: Tejun Heo Cc: Zefan Li Cc: Johannes Weiner Cc: cgroups@vger.kernel.org Cc: Alasdair Kergon Cc: Mike Snitzer Cc: dm-devel@redhat.com Cc: Mauro Carvalho Chehab Cc: linux-media@vger.kernel.org Cc: linux-mm@kvack.org Link: https://lore.kernel.org/r/20230129231053.20863-2-rdunlap@infradead.org Signed-off-by: Jonathan Corbet

docs: ftrace: always use canonical ftrace path

2023-01-31T21:02:30Z

The canonical location for the tracefs filesystem is at /sys/kernel/tracing. But, from Documentation/trace/ftrace.rst: Before 4.1, all ftrace tracing control files were within the debugfs file system, which is typically located at /sys/kernel/debug/tracing. For backward compatibility, when mounting the debugfs file system, the tracefs file system will be automatically mounted at: /sys/kernel/debug/tracing Many parts of Documentation still reference this older debugfs path, so let's update them to avoid confusion. Signed-off-by: Ross Zwisler Reviewed-by: Steven Rostedt (Google) Link: https://lore.kernel.org/r/20230125213251.2013791-1-zwisler@google.com Signed-off-by: Jonathan Corbet