On Thu, Jan 27, 2022 at 8:33 PM Ricardo Neri <ricardo.neri-calderon@xxxxxxxxxxxxxxx> wrote: > > Hi, > > This is v5 of this patchset after having incorporated the feedback from > reviewers. Please find v1, v2, v3, and v4 in [1], [2], [3], and [4], > respectively. > > The Intel Hardware Feedback Interface (HFI) [5] provides information about > the performance and energy efficiency of each CPU in the system. It uses a > table that is shared between hardware and the operating system. The > contents of the table may be updated as a result of changes in the > operating conditions of the system (e.g., reaching a thermal limit) or the > action of external factors (e.g., changes in the thermal design power). > > The information that HFI provides are specified as numeric, unit-less > capabilities relative to other CPUs in the system. These capabilities have > a range of [0-255] where higher numbers represent higher capabilities. > Energy efficiency and performance are reported in separate capabilities. > If either the performance or energy capabilities efficiency of a CPU are 0, > the hardware recommends to not schedule any tasks on such CPU for > performance, energy efficiency or thermal reasons, respectively. > > The kernel or user space may use the information from the HFI to modify > task placement and/or adjust power limits. This patchset focuses on the > user space. The thermal notification framework is extended to relay > updates of CPU capacity. Thus, a userspace daemon can affinitize workloads > to certain CPUs and/or offline CPUs whose capabilities are zero. > > The frequency of HFI updates is specific to each processor model. On some > systems, there is just a single HFI update at boot. On other systems, there > may be updates every tens of milliseconds. In order to not overwhelm > userspace with too many updates, they are limited to one update every > CONFIG_HZ jiffies. > > Thanks and BR, > Ricardo > > [1]. https://lore.kernel.org/lkml/20211106013312.26698-1-ricardo.neri-calderon@xxxxxxxxxxxxxxx/ > [2]. https://lore.kernel.org/lkml/20211220151438.1196-1-ricardo.neri-calderon@xxxxxxxxxxxxxxx/ > [3]. https://lore.kernel.org/lkml/20220106025059.25847-8-ricardo.neri-calderon@xxxxxxxxxxxxxxx/ > [4]. https://lore.kernel.org/lkml/20220108034743.31277-1-ricardo.neri-calderon@xxxxxxxxxxxxxxx/ > [5]. https://www.intel.com/sdm > > Changes since v4: > ++ Unchanged patches: 1, 2. > * Reworded description hfi_instance::hdr and hfi_instance::data. > (Patch 3; Srinivas) > * Call intel_hfi_online() before enabling the thermal vector at the > local APIC is enabled. This makes sure that a CPU has an associated > HFI instance when an HFI event happens. Reworded the commit message to > reflect this change. (Patch 4; Srinivas) > * Set hfi_instances to NULL if we fail to allocate memory for > hfi_instance::cpus. (Patch 4; Srinivas) > * Delayed initialization of local variables until after the check for a > non-NULL hfi_instances in intel_hfi_online(). (Patch 4; Srinivas) > * Optimized the error path in init_hfi_init() to not needlessly > free the memory of cpumasks that have not been allocated. (Patch 4; > Srinivas) > * Removed pointless checks for X86_FEATURE_HFI in > intel_hfi_[on|off]line(). It is sufficient to check for a non-NULL > hfi_instances or a CPU's hfi_instance. (Patch 4) > * Added a dedicated (i.e., not system_wq) workqueue to process HFI updates. > Reworded commit message accordingly. (Patch 5; Rafael) > * Repurposed comment on possibly receiving an HFI event with a NULL > hfi_cpu_info::instance. Patch 4 fixed this potential issue. Instead, > add a debug statement. (Patch 5; Srinivas) > * Wrapped check for NULL hfi_cpu_info::instance in the unlikely macro. > (Patch 5; Srinivas) > * Renamed struct cpu_capability as struct thermal_genl_cpu_caps. > (Patch 6; Rafael) > * Removed automatic variable ret from > thermal_genl_event_cpu_capability_change() and instead always return > -EMSGSIZE on error. (Patch 6; Rafael) > * Reworked parsing of HFI capabilities into chunks of > HFI_MAX_THERM_NOTIFY_COUNT CPUs at a time to reduce the time > we spend with interrupts disabled. (Patch7; Srinivas) > * Protected hfi_instance::cpus when iterating over them. (Patch 7; > Rafael) All patches in the series look good to me now, so I will be queuing it up for 5.18 unless there are any objections or concerns. Thanks!
