From cafb47be3f38ad81306bf894e743bebc2ccf66ab Mon Sep 17 00:00:00 2001 From: Kaushlendra Kumar Date: Sat, 9 Aug 2025 10:35:15 +0530 Subject: [PATCH 1/9] tools/power turbostat: Fix incorrect sorting of PMT telemetry The pmt_telemdir_sort() comparison function was returning a boolean value (0 or 1) instead of the required negative, zero, or positive value for proper sorting. This caused unpredictable and incorrect ordering of telemetry directories named telem0, telem1, ..., telemN. Update the comparison logic to return -1, 0, or 1 based on the numerical value extracted from the directory name, ensuring correct numerical ordering when using scandir. This change improves stability and correctness when iterating PMT telemetry directories. Signed-off-by: Kaushlendra Kumar Signed-off-by: Len Brown --- tools/power/x86/turbostat/turbostat.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/tools/power/x86/turbostat/turbostat.c b/tools/power/x86/turbostat/turbostat.c index 5230e072e414..b391196c3e90 100644 --- a/tools/power/x86/turbostat/turbostat.c +++ b/tools/power/x86/turbostat/turbostat.c @@ -1649,7 +1649,7 @@ int pmt_telemdir_sort(const struct dirent **a, const struct dirent **b) sscanf((*a)->d_name, "telem%u", &aidx); sscanf((*b)->d_name, "telem%u", &bidx); - return aidx >= bidx; + return (aidx > bidx) ? 1 : (aidx < bidx) ? -1 : 0; } const struct dirent *pmt_diriter_next(struct pmt_diriter_t *iter) From 62127655b7ab7b8c2997041aca48a81bf5c6da0c Mon Sep 17 00:00:00 2001 From: Kaushlendra Kumar Date: Wed, 13 Aug 2025 12:32:08 +0530 Subject: [PATCH 2/9] tools/power x86_energy_perf_policy: Fix incorrect fopen mode usage The fopen_or_die() function was previously hardcoded to open files in read-only mode ("r"), ignoring the mode parameter passed to it. This patch corrects fopen_or_die() to use the provided mode argument, allowing for flexible file access as intended. Additionally, the call to fopen_or_die() in err_on_hypervisor() incorrectly used the mode "ro", which is not a valid fopen mode. This is fixed to use the correct "r" mode. Signed-off-by: Kaushlendra Kumar Signed-off-by: Len Brown --- .../power/x86/x86_energy_perf_policy/x86_energy_perf_policy.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/tools/power/x86/x86_energy_perf_policy/x86_energy_perf_policy.c b/tools/power/x86/x86_energy_perf_policy/x86_energy_perf_policy.c index ebda9c366b2b..c883f211dbcc 100644 --- a/tools/power/x86/x86_energy_perf_policy/x86_energy_perf_policy.c +++ b/tools/power/x86/x86_energy_perf_policy/x86_energy_perf_policy.c @@ -630,7 +630,7 @@ void cmdline(int argc, char **argv) */ FILE *fopen_or_die(const char *path, const char *mode) { - FILE *filep = fopen(path, "r"); + FILE *filep = fopen(path, mode); if (!filep) err(1, "%s: open failed", path); @@ -644,7 +644,7 @@ void err_on_hypervisor(void) char *buffer; /* On VMs /proc/cpuinfo contains a "flags" entry for hypervisor */ - cpuinfo = fopen_or_die("/proc/cpuinfo", "ro"); + cpuinfo = fopen_or_die("/proc/cpuinfo", "r"); buffer = malloc(4096); if (!buffer) { From b6b42a6051b203bb1d78bf6518007e5dc8b62fc4 Mon Sep 17 00:00:00 2001 From: Len Brown Date: Fri, 19 Sep 2025 13:46:55 -0400 Subject: [PATCH 3/9] tools/power x86_energy_perf_policy: Enhance HWP enabled check Verify that all CPUs have HWP enabled, not just cpu0. Signed-off-by: Len Brown --- .../x86_energy_perf_policy.c | 46 +++++++++++++++---- 1 file changed, 37 insertions(+), 9 deletions(-) diff --git a/tools/power/x86/x86_energy_perf_policy/x86_energy_perf_policy.c b/tools/power/x86/x86_energy_perf_policy/x86_energy_perf_policy.c index c883f211dbcc..2bf0f878441e 100644 --- a/tools/power/x86/x86_energy_perf_policy/x86_energy_perf_policy.c +++ b/tools/power/x86/x86_energy_perf_policy/x86_energy_perf_policy.c @@ -4,7 +4,7 @@ * policy preference bias on recent X86 processors. */ /* - * Copyright (c) 2010 - 2017 Intel Corporation. + * Copyright (c) 2010 - 2025 Intel Corporation. * Len Brown */ @@ -517,7 +517,7 @@ void for_packages(unsigned long long pkg_set, int (func)(int)) void print_version(void) { - printf("x86_energy_perf_policy 17.05.11 (C) Len Brown \n"); + printf("x86_energy_perf_policy 2025.9.19 Len Brown \n"); } void cmdline(int argc, char **argv) @@ -1312,6 +1312,17 @@ void for_all_cpus_in_set(size_t set_size, cpu_set_t *cpu_set, int (func)(int)) if (CPU_ISSET_S(cpu_num, set_size, cpu_set)) func(cpu_num); } +int for_all_cpus_in_set_and(size_t set_size, cpu_set_t *cpu_set, int (func)(int)) +{ + int cpu_num; + int retval = 1; + + for (cpu_num = 0; cpu_num <= max_cpu_num; ++cpu_num) + if (CPU_ISSET_S(cpu_num, set_size, cpu_set)) + retval &= func(cpu_num); + + return retval; +} void init_data_structures(void) { @@ -1326,21 +1337,38 @@ void init_data_structures(void) for_all_proc_cpus(mark_cpu_present); } -/* clear has_hwp if it is not enable (or being enabled) */ - -void verify_hwp_is_enabled(void) +int is_hwp_enabled_on_cpu(int cpu_num) { unsigned long long msr; + int retval; + + /* MSR_PM_ENABLE[1] == 1 if HWP is enabled and MSRs visible */ + get_msr(cpu_num, MSR_PM_ENABLE, &msr); + retval = (msr & 1); + + if (verbose) + fprintf(stderr, "cpu%d: %sHWP\n", cpu_num, retval ? "" : "No-"); + + return retval; +} + +/* + * verify_hwp_is_enabled() + * + * Set (has_hwp=0) if no HWP feature or any of selected CPU set does not have HWP enabled + */ +void verify_hwp_is_enabled(void) +{ + int retval; if (!has_hwp) /* set in early_cpuid() */ return; - /* MSR_PM_ENABLE[1] == 1 if HWP is enabled and MSRs visible */ - get_msr(base_cpu, MSR_PM_ENABLE, &msr); - if ((msr & 1) == 0) { + retval = for_all_cpus_in_set_and(cpu_setsize, cpu_selected_set, is_hwp_enabled_on_cpu); + + if (retval == 0) { fprintf(stderr, "HWP can be enabled using '--hwp-enable'\n"); has_hwp = 0; - return; } } From c97c057d357c4b39b153e9e430bbf8976e05bd4e Mon Sep 17 00:00:00 2001 From: Len Brown Date: Fri, 19 Sep 2025 14:07:02 -0400 Subject: [PATCH 4/9] tools/power x86_energy_perf_policy: Enhance HWP enable On enabling HWP, preserve the reserved bits in MSR_PM_ENABLE. Also, skip writing the MSR_PM_ENABLE if HWP is already enabled. Signed-off-by: Len Brown --- .../x86_energy_perf_policy/x86_energy_perf_policy.c | 13 +++++++++---- 1 file changed, 9 insertions(+), 4 deletions(-) diff --git a/tools/power/x86/x86_energy_perf_policy/x86_energy_perf_policy.c b/tools/power/x86/x86_energy_perf_policy/x86_energy_perf_policy.c index 2bf0f878441e..70d7cdf0b07f 100644 --- a/tools/power/x86/x86_energy_perf_policy/x86_energy_perf_policy.c +++ b/tools/power/x86/x86_energy_perf_policy/x86_energy_perf_policy.c @@ -1166,13 +1166,18 @@ int update_hwp_request_pkg(int pkg) int enable_hwp_on_cpu(int cpu) { - unsigned long long msr; + unsigned long long old_msr, new_msr; - get_msr(cpu, MSR_PM_ENABLE, &msr); - put_msr(cpu, MSR_PM_ENABLE, 1); + get_msr(cpu, MSR_PM_ENABLE, &old_msr); + + if (old_msr & 1) + return 0; /* already enabled */ + + new_msr = old_msr | 1; + put_msr(cpu, MSR_PM_ENABLE, new_msr); if (verbose) - printf("cpu%d: MSR_PM_ENABLE old: %d new: %d\n", cpu, (unsigned int) msr, 1); + printf("cpu%d: MSR_PM_ENABLE old: %llX new: %llX\n", cpu, old_msr, new_msr); return 0; } From 8ef8fa829f8ad313f18d694c15874f85d693215d Mon Sep 17 00:00:00 2001 From: Len Brown Date: Fri, 19 Sep 2025 15:05:48 -0400 Subject: [PATCH 5/9] tools/power x86_energy_perf_policy: Prepare for MSR/sysfs refactoring Rename routines to make "_msr" and "_sysfs" access methods clear No functional change Signed-off-by: Len Brown --- .../x86_energy_perf_policy.c | 38 +++++++++---------- 1 file changed, 19 insertions(+), 19 deletions(-) diff --git a/tools/power/x86/x86_energy_perf_policy/x86_energy_perf_policy.c b/tools/power/x86/x86_energy_perf_policy/x86_energy_perf_policy.c index 70d7cdf0b07f..ce6fb8080105 100644 --- a/tools/power/x86/x86_energy_perf_policy/x86_energy_perf_policy.c +++ b/tools/power/x86/x86_energy_perf_policy/x86_energy_perf_policy.c @@ -809,7 +809,7 @@ void print_hwp_request_pkg(int pkg, struct msr_hwp_request *h, char *str) h->hwp_min, h->hwp_max, h->hwp_desired, h->hwp_epp, h->hwp_window, h->hwp_window & 0x7F, (h->hwp_window >> 7) & 0x7); } -void read_hwp_request(int cpu, struct msr_hwp_request *hwp_req, unsigned int msr_offset) +void read_hwp_request_msr(int cpu, struct msr_hwp_request *hwp_req, unsigned int msr_offset) { unsigned long long msr; @@ -823,7 +823,7 @@ void read_hwp_request(int cpu, struct msr_hwp_request *hwp_req, unsigned int msr hwp_req->hwp_use_pkg = (((msr) >> 42) & 0x1); } -void write_hwp_request(int cpu, struct msr_hwp_request *hwp_req, unsigned int msr_offset) +void write_hwp_request_msr(int cpu, struct msr_hwp_request *hwp_req, unsigned int msr_offset) { unsigned long long msr = 0; @@ -843,7 +843,7 @@ void write_hwp_request(int cpu, struct msr_hwp_request *hwp_req, unsigned int ms put_msr(cpu, msr_offset, msr); } -static int get_epb(int cpu) +static int get_epb_sysfs(int cpu) { char path[SYSFS_PATH_MAX]; char linebuf[3]; @@ -865,7 +865,7 @@ static int get_epb(int cpu) return (int)val; } -static int set_epb(int cpu, int val) +static int set_epb_sysfs(int cpu, int val) { char path[SYSFS_PATH_MAX]; char linebuf[3]; @@ -895,14 +895,14 @@ int print_cpu_msrs(int cpu) struct msr_hwp_cap cap; int epb; - epb = get_epb(cpu); + epb = get_epb_sysfs(cpu); if (epb >= 0) printf("cpu%d: EPB %u\n", cpu, (unsigned int) epb); if (!has_hwp) return 0; - read_hwp_request(cpu, &req, MSR_HWP_REQUEST); + read_hwp_request_msr(cpu, &req, MSR_HWP_REQUEST); print_hwp_request(cpu, &req, ""); read_hwp_cap(cpu, &cap, MSR_HWP_CAPABILITIES); @@ -919,7 +919,7 @@ int print_pkg_msrs(int pkg) if (!has_hwp) return 0; - read_hwp_request(first_cpu_in_pkg[pkg], &req, MSR_HWP_REQUEST_PKG); + read_hwp_request_msr(first_cpu_in_pkg[pkg], &req, MSR_HWP_REQUEST_PKG); print_hwp_request_pkg(pkg, &req, ""); if (has_hwp_notify) { @@ -1074,14 +1074,14 @@ int check_hwp_request_v_hwp_capabilities(int cpu, struct msr_hwp_request *req, s return 0; } -int update_hwp_request(int cpu) +int update_hwp_request_msr(int cpu) { struct msr_hwp_request req; struct msr_hwp_cap cap; int msr_offset = MSR_HWP_REQUEST; - read_hwp_request(cpu, &req, msr_offset); + read_hwp_request_msr(cpu, &req, msr_offset); if (debug) print_hwp_request(cpu, &req, "old: "); @@ -1111,15 +1111,15 @@ int update_hwp_request(int cpu) verify_hwp_req_self_consistency(cpu, &req); - write_hwp_request(cpu, &req, msr_offset); + write_hwp_request_msr(cpu, &req, msr_offset); if (debug) { - read_hwp_request(cpu, &req, msr_offset); + read_hwp_request_msr(cpu, &req, msr_offset); print_hwp_request(cpu, &req, "new: "); } return 0; } -int update_hwp_request_pkg(int pkg) +int update_hwp_request_pkg_msr(int pkg) { struct msr_hwp_request req; struct msr_hwp_cap cap; @@ -1127,7 +1127,7 @@ int update_hwp_request_pkg(int pkg) int msr_offset = MSR_HWP_REQUEST_PKG; - read_hwp_request(cpu, &req, msr_offset); + read_hwp_request_msr(cpu, &req, msr_offset); if (debug) print_hwp_request_pkg(pkg, &req, "old: "); @@ -1155,10 +1155,10 @@ int update_hwp_request_pkg(int pkg) verify_hwp_req_self_consistency(cpu, &req); - write_hwp_request(cpu, &req, msr_offset); + write_hwp_request_msr(cpu, &req, msr_offset); if (debug) { - read_hwp_request(cpu, &req, msr_offset); + read_hwp_request_msr(cpu, &req, msr_offset); print_hwp_request_pkg(pkg, &req, "new: "); } return 0; @@ -1188,8 +1188,8 @@ int update_cpu_msrs(int cpu) int epb; if (update_epb) { - epb = get_epb(cpu); - set_epb(cpu, new_epb); + epb = get_epb_sysfs(cpu); + set_epb_sysfs(cpu, new_epb); if (verbose) printf("cpu%d: ENERGY_PERF_BIAS old: %d new: %d\n", @@ -1229,7 +1229,7 @@ int update_cpu_msrs(int cpu) if (!hwp_update_enabled()) return 0; - update_hwp_request(cpu); + update_hwp_request_msr(cpu); return 0; } @@ -1587,7 +1587,7 @@ int main(int argc, char **argv) for_all_cpus_in_set(cpu_setsize, cpu_selected_set, update_sysfs); for_all_cpus_in_set(cpu_setsize, cpu_selected_set, update_cpu_msrs); } else if (pkg_selected_set) - for_packages(pkg_selected_set, update_hwp_request_pkg); + for_packages(pkg_selected_set, update_hwp_request_pkg_msr); return 0; } From f8241f5426eb9feb46a007341edd221ceaf73073 Mon Sep 17 00:00:00 2001 From: Len Brown Date: Fri, 19 Sep 2025 15:35:07 -0400 Subject: [PATCH 6/9] tools/power x86_energy_perf_policy: EPB access is only via sysfs Comprehend that EPB writes are now only via sysfs by moving it out of the _msr specific path. No functional change. Signed-off-by: Len Brown --- .../x86_energy_perf_policy.c | 27 ++++++++++++------- 1 file changed, 17 insertions(+), 10 deletions(-) diff --git a/tools/power/x86/x86_energy_perf_policy/x86_energy_perf_policy.c b/tools/power/x86/x86_energy_perf_policy/x86_energy_perf_policy.c index ce6fb8080105..fe10057bf9b7 100644 --- a/tools/power/x86/x86_energy_perf_policy/x86_energy_perf_policy.c +++ b/tools/power/x86/x86_energy_perf_policy/x86_energy_perf_policy.c @@ -1182,19 +1182,23 @@ int enable_hwp_on_cpu(int cpu) return 0; } +int update_cpu_epb_sysfs(int cpu) +{ + int epb; + + epb = get_epb_sysfs(cpu); + set_epb_sysfs(cpu, new_epb); + + if (verbose) + printf("cpu%d: ENERGY_PERF_BIAS old: %d new: %d\n", + cpu, epb, (unsigned int) new_epb); + + return 0; +} + int update_cpu_msrs(int cpu) { unsigned long long msr; - int epb; - - if (update_epb) { - epb = get_epb_sysfs(cpu); - set_epb_sysfs(cpu, new_epb); - - if (verbose) - printf("cpu%d: ENERGY_PERF_BIAS old: %d new: %d\n", - cpu, epb, (unsigned int) new_epb); - } if (update_turbo) { int turbo_is_present_and_disabled; @@ -1584,8 +1588,11 @@ int main(int argc, char **argv) /* update CPU set */ if (cpu_selected_set) { + if (update_epb) + for_all_cpus_in_set(cpu_setsize, cpu_selected_set, update_cpu_epb_sysfs); for_all_cpus_in_set(cpu_setsize, cpu_selected_set, update_sysfs); for_all_cpus_in_set(cpu_setsize, cpu_selected_set, update_cpu_msrs); + } else if (pkg_selected_set) for_packages(pkg_selected_set, update_hwp_request_pkg_msr); From 2734fdbc9bb8a3aeb309ba0d62212d7f53f30bc7 Mon Sep 17 00:00:00 2001 From: Len Brown Date: Fri, 19 Sep 2025 15:56:46 -0400 Subject: [PATCH 7/9] tools/power x86_energy_perf_policy: Prefer driver HWP limits When we are successful in using cpufreq min/max limits, skip setting the raw MSR limits entirely. This is necessary to avoid undoing any modification that the cpufreq driver makes to our sysfs request. eg. intel_pstate may take our request for a limit that is valid according to HWP.CAP.MIN/MAX and clip it to be within the range available in PLATFORM_INFO. Signed-off-by: Len Brown --- .../x86_energy_perf_policy/x86_energy_perf_policy.c | 13 +++++++++---- 1 file changed, 9 insertions(+), 4 deletions(-) diff --git a/tools/power/x86/x86_energy_perf_policy/x86_energy_perf_policy.c b/tools/power/x86/x86_energy_perf_policy/x86_energy_perf_policy.c index fe10057bf9b7..884a4c746f32 100644 --- a/tools/power/x86/x86_energy_perf_policy/x86_energy_perf_policy.c +++ b/tools/power/x86/x86_energy_perf_policy/x86_energy_perf_policy.c @@ -62,6 +62,7 @@ unsigned char turbo_update_value; unsigned char update_hwp_epp; unsigned char update_hwp_min; unsigned char update_hwp_max; +unsigned char hwp_limits_done_via_sysfs; unsigned char update_hwp_desired; unsigned char update_hwp_window; unsigned char update_hwp_use_pkg; @@ -951,8 +952,10 @@ int ratio_2_sysfs_khz(int ratio) } /* * If HWP is enabled and cpufreq sysfs attribtes are present, - * then update sysfs, so that it will not become - * stale when we write to MSRs. + * then update via sysfs. The intel_pstate driver may modify (clip) + * this request, say, when HWP_CAP is outside of PLATFORM_INFO limits, + * and the driver-chosen value takes precidence. + * * (intel_pstate's max_perf_pct and min_perf_pct will follow cpufreq, * so we don't have to touch that.) */ @@ -1007,6 +1010,8 @@ int update_sysfs(int cpu) if (update_hwp_max) update_cpufreq_scaling_freq(1, cpu, req_update.hwp_max); + hwp_limits_done_via_sysfs = 1; + return 0; } @@ -1085,10 +1090,10 @@ int update_hwp_request_msr(int cpu) if (debug) print_hwp_request(cpu, &req, "old: "); - if (update_hwp_min) + if (update_hwp_min && !hwp_limits_done_via_sysfs) req.hwp_min = req_update.hwp_min; - if (update_hwp_max) + if (update_hwp_max && !hwp_limits_done_via_sysfs) req.hwp_max = req_update.hwp_max; if (update_hwp_desired) From a648e0892ccd8c2168c2deae7e12e18a8d596730 Mon Sep 17 00:00:00 2001 From: Len Brown Date: Fri, 19 Sep 2025 22:30:18 -0400 Subject: [PATCH 8/9] tools/power x86_energy_perf_policy: Add make snapshot target $ make snapshot creates x86_energy_perf_policy-$(DATE).tar.gz Which can be transported to a target machine without needing a kernel tree to build on the target. Useful for creating debug versions. Signed-off-by: Len Brown --- .../power/x86/x86_energy_perf_policy/Makefile | 29 ++++++++++++++++++- 1 file changed, 28 insertions(+), 1 deletion(-) diff --git a/tools/power/x86/x86_energy_perf_policy/Makefile b/tools/power/x86/x86_energy_perf_policy/Makefile index 666b325a62a2..d18284667400 100644 --- a/tools/power/x86/x86_energy_perf_policy/Makefile +++ b/tools/power/x86/x86_energy_perf_policy/Makefile @@ -1,8 +1,12 @@ # SPDX-License-Identifier: GPL-2.0 CC = $(CROSS_COMPILE)gcc -BUILD_OUTPUT := $(CURDIR) +BUILD_OUTPUT := $(CURDIR) PREFIX := /usr DESTDIR := +DAY := $(shell date +%Y.%m.%d) +SNAPSHOT = x86_energy_perf_policy-$(DAY) + + ifeq ("$(origin O)", "command line") BUILD_OUTPUT := $(O) @@ -27,3 +31,26 @@ install : x86_energy_perf_policy install -d $(DESTDIR)$(PREFIX)/share/man/man8 install -m 644 x86_energy_perf_policy.8 $(DESTDIR)$(PREFIX)/share/man/man8 +snapshot: x86_energy_perf_policy + @rm -rf $(SNAPSHOT) + @mkdir $(SNAPSHOT) + @cp x86_energy_perf_policy Makefile x86_energy_perf_policy.c x86_energy_perf_policy.8 $(SNAPSHOT) + + @sed -e 's/^#include /#include "bits.h"/' -e 's/u64/unsigned long long/' ../../../../arch/x86/include/asm/msr-index.h > $(SNAPSHOT)/msr-index.h + @echo '#define ARRAY_SIZE(arr) (sizeof(arr) / sizeof((arr)[0]))' >> $(SNAPSHOT)/msr-index.h + @echo "#define BIT(x) (1 << (x))" > $(SNAPSHOT)/bits.h + @echo "#define BIT_ULL(nr) (1ULL << (nr))" >> $(SNAPSHOT)/bits.h + @echo "#define GENMASK(h, l) (((~0UL) << (l)) & (~0UL >> (sizeof(long) * 8 - 1 - (h))))" >> $(SNAPSHOT)/bits.h + @echo "#define GENMASK_ULL(h, l) (((~0ULL) << (l)) & (~0ULL >> (sizeof(long long) * 8 - 1 - (h))))" >> $(SNAPSHOT)/bits.h + + @echo '#define BUILD_BUG_ON(cond) do { enum { compile_time_check ## __COUNTER__ = 1/(!(cond)) }; } while (0)' > $(SNAPSHOT)/build_bug.h + @echo '#define __must_be_array(arr) 0' >> $(SNAPSHOT)/build_bug.h + + @echo PWD=. > $(SNAPSHOT)/Makefile + @echo "CFLAGS += -DMSRHEADER='\"msr-index.h\"'" >> $(SNAPSHOT)/Makefile + @echo "CFLAGS += -DBUILD_BUG_HEADER='\"build_bug.h\"'" >> $(SNAPSHOT)/Makefile + @sed -e's/.*MSRHEADER.*//' Makefile >> $(SNAPSHOT)/Makefile + + @rm -f $(SNAPSHOT).tar.gz + tar cvzf $(SNAPSHOT).tar.gz $(SNAPSHOT) + From 66f430522452fe1a8a0fd2198cf9f335125acbfc Mon Sep 17 00:00:00 2001 From: Len Brown Date: Wed, 24 Sep 2025 11:50:29 -0400 Subject: [PATCH 9/9] tools/power x86_energy_perf_policy.8: Emphasize preference for SW interfaces This tool was originally written when Linux had no standard interface for EPB, or HWP support. Retain the capability to manage a system w/o any kernel PM support, but prefer the standard kernel interfaces, when avaialble. (not doing so led to a confusing conflict between a p-state limit request made via cpufreq and modified by the intel-pstate driver, versus the raw MSR write made by this utility) Signed-off-by: Len Brown --- .../x86_energy_perf_policy.8 | 15 +++++++++++---- 1 file changed, 11 insertions(+), 4 deletions(-) diff --git a/tools/power/x86/x86_energy_perf_policy/x86_energy_perf_policy.8 b/tools/power/x86/x86_energy_perf_policy/x86_energy_perf_policy.8 index 78c6361898b1..0aa981c18e56 100644 --- a/tools/power/x86/x86_energy_perf_policy/x86_energy_perf_policy.8 +++ b/tools/power/x86/x86_energy_perf_policy/x86_energy_perf_policy.8 @@ -2,7 +2,7 @@ .\" Distributed under the GPL, Copyleft 1994. .TH X86_ENERGY_PERF_POLICY 8 .SH NAME -x86_energy_perf_policy \- Manage Energy vs. Performance Policy via x86 Model Specific Registers +x86_energy_perf_policy \- Manage Energy vs. Performance Policy .SH SYNOPSIS .B x86_energy_perf_policy .RB "[ options ] [ scope ] [field \ value]" @@ -19,9 +19,14 @@ x86_energy_perf_policy \- Manage Energy vs. Performance Policy via x86 Model Spe .SH DESCRIPTION \fBx86_energy_perf_policy\fP displays and updates energy-performance policy settings specific to -Intel Architecture Processors. Settings are accessed via Model Specific Register (MSR) -updates, no matter if the Linux cpufreq sub-system is enabled or not. +Intel Architecture Processors. It summarizes settings available +in standard Linux interfaces (eg. cpufreq), +and also decodes underlying Model Specific Register (MSRs). +While \fBx86_energy_perf_policy\fP can manage energy-performance policy +using only MSR access, it prefers standard +Linux kernel interfaces, when they are available. +.SH BACKGROUND Policy in MSR_IA32_ENERGY_PERF_BIAS (EPB) may affect a wide range of hardware decisions, such as how aggressively the hardware enters and exits CPU idle states (C-states) @@ -200,7 +205,9 @@ runs only as root. .SH FILES .ta .nf -/dev/cpu/*/msr +EPB: /sys/devices/system/cpu/cpu*/power/energy_perf_bias +EPP: /sys/devices/system/cpu/cpu*/cpufreq/energy_performance_preference +MSR: /dev/cpu/*/msr .fi .SH "SEE ALSO" .nf