Loading Documentation/ABI/testing/procfs-concurrent_time 0 → 100644 +16 −0 Original line number Diff line number Diff line What: /proc/uid_concurrent_active_time Date: December 2018 Contact: Connor O'Brien <connoro@google.com> Description: The /proc/uid_concurrent_active_time file displays aggregated cputime numbers for each uid, broken down by the total number of cores that were active while the uid's task was running. What: /proc/uid_concurrent_policy_time Date: December 2018 Contact: Connor O'Brien <connoro@google.com> Description: The /proc/uid_concurrent_policy_time file displays aggregated cputime numbers for each uid, broken down based on the cpufreq policy of the core used by the uid's task and the number of cores associated with that policy that were active while the uid's task was running. Documentation/filesystems/overlayfs.txt +23 −0 Original line number Diff line number Diff line Loading @@ -102,6 +102,29 @@ Only the lists of names from directories are merged. Other content such as metadata and extended attributes are reported for the upper directory only. These attributes of the lower directory are hidden. credentials ----------- By default, all access to the upper, lower and work directories is the recorded mounter's MAC and DAC credentials. The incoming accesses are checked against the caller's credentials. In the case where caller MAC or DAC credentials do not overlap, a use case available in older versions of the driver, the override_creds mount flag can be turned off and help when the use pattern has caller with legitimate credentials where the mounter does not. Several unintended side effects will occur though. The caller without certain key capabilities or lower privilege will not always be able to delete files or directories, create nodes, or search some restricted directories. The ability to search and read a directory entry is spotty as a result of the cache mechanism not retesting the credentials because of the assumption, a privileged caller can fill cache, then a lower privilege can read the directory cache. The uneven security model where cache, upperdir and workdir are opened at privilege, but accessed without creating a form of privilege escalation, should only be used with strict understanding of the side effects and of the security policies. whiteouts and opaque directories -------------------------------- Loading Documentation/power/energy-model.txt 0 → 100644 +169 −0 Original line number Diff line number Diff line ==================== Energy Model of CPUs ==================== 1. Overview ----------- The Energy Model (EM) framework serves as an interface between drivers knowing the power consumed by CPUs at various performance levels, and the kernel subsystems willing to use that information to make energy-aware decisions. The source of the information about the power consumed by CPUs can vary greatly from one platform to another. These power costs can be estimated using devicetree data in some cases. In others, the firmware will know better. Alternatively, userspace might be best positioned. And so on. In order to avoid each and every client subsystem to re-implement support for each and every possible source of information on its own, the EM framework intervenes as an abstraction layer which standardizes the format of power cost tables in the kernel, hence enabling to avoid redundant work. The figure below depicts an example of drivers (Arm-specific here, but the approach is applicable to any architecture) providing power costs to the EM framework, and interested clients reading the data from it. +---------------+ +-----------------+ +---------------+ | Thermal (IPA) | | Scheduler (EAS) | | Other | +---------------+ +-----------------+ +---------------+ | | em_pd_energy() | | | em_cpu_get() | +---------+ | +---------+ | | | v v v +---------------------+ | Energy Model | | Framework | +---------------------+ ^ ^ ^ | | | em_register_perf_domain() +----------+ | +---------+ | | | +---------------+ +---------------+ +--------------+ | cpufreq-dt | | arm_scmi | | Other | +---------------+ +---------------+ +--------------+ ^ ^ ^ | | | +--------------+ +---------------+ +--------------+ | Device Tree | | Firmware | | ? | +--------------+ +---------------+ +--------------+ The EM framework manages power cost tables per 'performance domain' in the system. A performance domain is a group of CPUs whose performance is scaled together. Performance domains generally have a 1-to-1 mapping with CPUFreq policies. All CPUs in a performance domain are required to have the same micro-architecture. CPUs in different performance domains can have different micro-architectures. 2. Core APIs ------------ 2.1 Config options CONFIG_ENERGY_MODEL must be enabled to use the EM framework. 2.2 Registration of performance domains Drivers are expected to register performance domains into the EM framework by calling the following API: int em_register_perf_domain(cpumask_t *span, unsigned int nr_states, struct em_data_callback *cb); Drivers must specify the CPUs of the performance domains using the cpumask argument, and provide a callback function returning <frequency, power> tuples for each capacity state. The callback function provided by the driver is free to fetch data from any relevant location (DT, firmware, ...), and by any mean deemed necessary. See Section 3. for an example of driver implementing this callback, and kernel/power/energy_model.c for further documentation on this API. 2.3 Accessing performance domains Subsystems interested in the energy model of a CPU can retrieve it using the em_cpu_get() API. The energy model tables are allocated once upon creation of the performance domains, and kept in memory untouched. The energy consumed by a performance domain can be estimated using the em_pd_energy() API. The estimation is performed assuming that the schedutil CPUfreq governor is in use. More details about the above APIs can be found in include/linux/energy_model.h. 3. Example driver ----------------- This section provides a simple example of a CPUFreq driver registering a performance domain in the Energy Model framework using the (fake) 'foo' protocol. The driver implements an est_power() function to be provided to the EM framework. -> drivers/cpufreq/foo_cpufreq.c 01 static int est_power(unsigned long *mW, unsigned long *KHz, int cpu) 02 { 03 long freq, power; 04 05 /* Use the 'foo' protocol to ceil the frequency */ 06 freq = foo_get_freq_ceil(cpu, *KHz); 07 if (freq < 0); 08 return freq; 09 10 /* Estimate the power cost for the CPU at the relevant freq. */ 11 power = foo_estimate_power(cpu, freq); 12 if (power < 0); 13 return power; 14 15 /* Return the values to the EM framework */ 16 *mW = power; 17 *KHz = freq; 18 19 return 0; 20 } 21 22 static int foo_cpufreq_init(struct cpufreq_policy *policy) 23 { 24 struct em_data_callback em_cb = EM_DATA_CB(est_power); 25 int nr_opp, ret; 26 27 /* Do the actual CPUFreq init work ... */ 28 ret = do_foo_cpufreq_init(policy); 29 if (ret) 30 return ret; 31 32 /* Find the number of OPPs for this policy */ 33 nr_opp = foo_get_nr_opp(policy); 34 35 /* And register the new performance domain */ 36 em_register_perf_domain(policy->cpus, nr_opp, &em_cb); 37 38 return 0; 39 } 4. Support for legacy Energy Models (DEPRECATED) ------------------------------------------------ The Android kernel version 4.14 and before used a different type of EM for EAS, referred to as the 'legacy' EM. The legacy EM relies on the out-of-tree 'sched-energy-costs' devicetree bindings to provide the kernel with power costs. The usage of such bindings in Android has now been DEPRECATED in favour of the mainline equivalents. The currently supported alternatives to populate the EM include: - using a firmware-based solution such as Arm SCMI (supported in drivers/cpufreq/scmi-cpufreq.c); - using the 'dynamic-power-coefficient' devicetree binding together with PM_OPP. See the of_dev_pm_opp_get_cpu_power() helper in PM_OPP, and the reference implementation in drivers/cpufreq/cpufreq-dt.c. In order to ease the transition to the new EM format, Android 4.19 also provides a compatibility driver able to load a legacy EM from DT into the EM framework. *** Please note that THIS FEATURE WILL NOT BE AVAILABLE in future Android kernels, and as such it must be considered only as a temporary workaround. *** If you know what you're doing and still want to use this driver, you need to set CONFIG_LEGACY_ENERGY_MODEL_DT=y in your kernel configuration to enable it. Loading
Documentation/ABI/testing/procfs-concurrent_time 0 → 100644 +16 −0 Original line number Diff line number Diff line What: /proc/uid_concurrent_active_time Date: December 2018 Contact: Connor O'Brien <connoro@google.com> Description: The /proc/uid_concurrent_active_time file displays aggregated cputime numbers for each uid, broken down by the total number of cores that were active while the uid's task was running. What: /proc/uid_concurrent_policy_time Date: December 2018 Contact: Connor O'Brien <connoro@google.com> Description: The /proc/uid_concurrent_policy_time file displays aggregated cputime numbers for each uid, broken down based on the cpufreq policy of the core used by the uid's task and the number of cores associated with that policy that were active while the uid's task was running.
Documentation/filesystems/overlayfs.txt +23 −0 Original line number Diff line number Diff line Loading @@ -102,6 +102,29 @@ Only the lists of names from directories are merged. Other content such as metadata and extended attributes are reported for the upper directory only. These attributes of the lower directory are hidden. credentials ----------- By default, all access to the upper, lower and work directories is the recorded mounter's MAC and DAC credentials. The incoming accesses are checked against the caller's credentials. In the case where caller MAC or DAC credentials do not overlap, a use case available in older versions of the driver, the override_creds mount flag can be turned off and help when the use pattern has caller with legitimate credentials where the mounter does not. Several unintended side effects will occur though. The caller without certain key capabilities or lower privilege will not always be able to delete files or directories, create nodes, or search some restricted directories. The ability to search and read a directory entry is spotty as a result of the cache mechanism not retesting the credentials because of the assumption, a privileged caller can fill cache, then a lower privilege can read the directory cache. The uneven security model where cache, upperdir and workdir are opened at privilege, but accessed without creating a form of privilege escalation, should only be used with strict understanding of the side effects and of the security policies. whiteouts and opaque directories -------------------------------- Loading
Documentation/power/energy-model.txt 0 → 100644 +169 −0 Original line number Diff line number Diff line ==================== Energy Model of CPUs ==================== 1. Overview ----------- The Energy Model (EM) framework serves as an interface between drivers knowing the power consumed by CPUs at various performance levels, and the kernel subsystems willing to use that information to make energy-aware decisions. The source of the information about the power consumed by CPUs can vary greatly from one platform to another. These power costs can be estimated using devicetree data in some cases. In others, the firmware will know better. Alternatively, userspace might be best positioned. And so on. In order to avoid each and every client subsystem to re-implement support for each and every possible source of information on its own, the EM framework intervenes as an abstraction layer which standardizes the format of power cost tables in the kernel, hence enabling to avoid redundant work. The figure below depicts an example of drivers (Arm-specific here, but the approach is applicable to any architecture) providing power costs to the EM framework, and interested clients reading the data from it. +---------------+ +-----------------+ +---------------+ | Thermal (IPA) | | Scheduler (EAS) | | Other | +---------------+ +-----------------+ +---------------+ | | em_pd_energy() | | | em_cpu_get() | +---------+ | +---------+ | | | v v v +---------------------+ | Energy Model | | Framework | +---------------------+ ^ ^ ^ | | | em_register_perf_domain() +----------+ | +---------+ | | | +---------------+ +---------------+ +--------------+ | cpufreq-dt | | arm_scmi | | Other | +---------------+ +---------------+ +--------------+ ^ ^ ^ | | | +--------------+ +---------------+ +--------------+ | Device Tree | | Firmware | | ? | +--------------+ +---------------+ +--------------+ The EM framework manages power cost tables per 'performance domain' in the system. A performance domain is a group of CPUs whose performance is scaled together. Performance domains generally have a 1-to-1 mapping with CPUFreq policies. All CPUs in a performance domain are required to have the same micro-architecture. CPUs in different performance domains can have different micro-architectures. 2. Core APIs ------------ 2.1 Config options CONFIG_ENERGY_MODEL must be enabled to use the EM framework. 2.2 Registration of performance domains Drivers are expected to register performance domains into the EM framework by calling the following API: int em_register_perf_domain(cpumask_t *span, unsigned int nr_states, struct em_data_callback *cb); Drivers must specify the CPUs of the performance domains using the cpumask argument, and provide a callback function returning <frequency, power> tuples for each capacity state. The callback function provided by the driver is free to fetch data from any relevant location (DT, firmware, ...), and by any mean deemed necessary. See Section 3. for an example of driver implementing this callback, and kernel/power/energy_model.c for further documentation on this API. 2.3 Accessing performance domains Subsystems interested in the energy model of a CPU can retrieve it using the em_cpu_get() API. The energy model tables are allocated once upon creation of the performance domains, and kept in memory untouched. The energy consumed by a performance domain can be estimated using the em_pd_energy() API. The estimation is performed assuming that the schedutil CPUfreq governor is in use. More details about the above APIs can be found in include/linux/energy_model.h. 3. Example driver ----------------- This section provides a simple example of a CPUFreq driver registering a performance domain in the Energy Model framework using the (fake) 'foo' protocol. The driver implements an est_power() function to be provided to the EM framework. -> drivers/cpufreq/foo_cpufreq.c 01 static int est_power(unsigned long *mW, unsigned long *KHz, int cpu) 02 { 03 long freq, power; 04 05 /* Use the 'foo' protocol to ceil the frequency */ 06 freq = foo_get_freq_ceil(cpu, *KHz); 07 if (freq < 0); 08 return freq; 09 10 /* Estimate the power cost for the CPU at the relevant freq. */ 11 power = foo_estimate_power(cpu, freq); 12 if (power < 0); 13 return power; 14 15 /* Return the values to the EM framework */ 16 *mW = power; 17 *KHz = freq; 18 19 return 0; 20 } 21 22 static int foo_cpufreq_init(struct cpufreq_policy *policy) 23 { 24 struct em_data_callback em_cb = EM_DATA_CB(est_power); 25 int nr_opp, ret; 26 27 /* Do the actual CPUFreq init work ... */ 28 ret = do_foo_cpufreq_init(policy); 29 if (ret) 30 return ret; 31 32 /* Find the number of OPPs for this policy */ 33 nr_opp = foo_get_nr_opp(policy); 34 35 /* And register the new performance domain */ 36 em_register_perf_domain(policy->cpus, nr_opp, &em_cb); 37 38 return 0; 39 } 4. Support for legacy Energy Models (DEPRECATED) ------------------------------------------------ The Android kernel version 4.14 and before used a different type of EM for EAS, referred to as the 'legacy' EM. The legacy EM relies on the out-of-tree 'sched-energy-costs' devicetree bindings to provide the kernel with power costs. The usage of such bindings in Android has now been DEPRECATED in favour of the mainline equivalents. The currently supported alternatives to populate the EM include: - using a firmware-based solution such as Arm SCMI (supported in drivers/cpufreq/scmi-cpufreq.c); - using the 'dynamic-power-coefficient' devicetree binding together with PM_OPP. See the of_dev_pm_opp_get_cpu_power() helper in PM_OPP, and the reference implementation in drivers/cpufreq/cpufreq-dt.c. In order to ease the transition to the new EM format, Android 4.19 also provides a compatibility driver able to load a legacy EM from DT into the EM framework. *** Please note that THIS FEATURE WILL NOT BE AVAILABLE in future Android kernels, and as such it must be considered only as a temporary workaround. *** If you know what you're doing and still want to use this driver, you need to set CONFIG_LEGACY_ENERGY_MODEL_DT=y in your kernel configuration to enable it.
