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-rw-r--r--Documentation/admin-guide/acpi/cppc_sysfs.rst (renamed from Documentation/acpi/cppc_sysfs.txt)71
-rw-r--r--Documentation/admin-guide/acpi/index.rst1
2 files changed, 40 insertions, 32 deletions
diff --git a/Documentation/acpi/cppc_sysfs.txt b/Documentation/admin-guide/acpi/cppc_sysfs.rst
index f20fb445135d..a4b99afbe331 100644
--- a/Documentation/acpi/cppc_sysfs.txt
+++ b/Documentation/admin-guide/acpi/cppc_sysfs.rst
@@ -1,5 +1,11 @@
1.. SPDX-License-Identifier: GPL-2.0
1 2
2 Collaborative Processor Performance Control (CPPC) 3==================================================
4Collaborative Processor Performance Control (CPPC)
5==================================================
6
7CPPC
8====
3 9
4CPPC defined in the ACPI spec describes a mechanism for the OS to manage the 10CPPC defined in the ACPI spec describes a mechanism for the OS to manage the
5performance of a logical processor on a contigious and abstract performance 11performance of a logical processor on a contigious and abstract performance
@@ -10,31 +16,28 @@ For more details on CPPC please refer to the ACPI specification at:
10 16
11http://uefi.org/specifications 17http://uefi.org/specifications
12 18
13Some of the CPPC registers are exposed via sysfs under: 19Some of the CPPC registers are exposed via sysfs under::
14
15/sys/devices/system/cpu/cpuX/acpi_cppc/
16
17for each cpu X
18 20
19-------------------------------------------------------------------------------- 21 /sys/devices/system/cpu/cpuX/acpi_cppc/
20 22
21$ ls -lR /sys/devices/system/cpu/cpu0/acpi_cppc/ 23for each cpu X::
22/sys/devices/system/cpu/cpu0/acpi_cppc/:
23total 0
24-r--r--r-- 1 root root 65536 Mar 5 19:38 feedback_ctrs
25-r--r--r-- 1 root root 65536 Mar 5 19:38 highest_perf
26-r--r--r-- 1 root root 65536 Mar 5 19:38 lowest_freq
27-r--r--r-- 1 root root 65536 Mar 5 19:38 lowest_nonlinear_perf
28-r--r--r-- 1 root root 65536 Mar 5 19:38 lowest_perf
29-r--r--r-- 1 root root 65536 Mar 5 19:38 nominal_freq
30-r--r--r-- 1 root root 65536 Mar 5 19:38 nominal_perf
31-r--r--r-- 1 root root 65536 Mar 5 19:38 reference_perf
32-r--r--r-- 1 root root 65536 Mar 5 19:38 wraparound_time
33 24
34-------------------------------------------------------------------------------- 25 $ ls -lR /sys/devices/system/cpu/cpu0/acpi_cppc/
26 /sys/devices/system/cpu/cpu0/acpi_cppc/:
27 total 0
28 -r--r--r-- 1 root root 65536 Mar 5 19:38 feedback_ctrs
29 -r--r--r-- 1 root root 65536 Mar 5 19:38 highest_perf
30 -r--r--r-- 1 root root 65536 Mar 5 19:38 lowest_freq
31 -r--r--r-- 1 root root 65536 Mar 5 19:38 lowest_nonlinear_perf
32 -r--r--r-- 1 root root 65536 Mar 5 19:38 lowest_perf
33 -r--r--r-- 1 root root 65536 Mar 5 19:38 nominal_freq
34 -r--r--r-- 1 root root 65536 Mar 5 19:38 nominal_perf
35 -r--r--r-- 1 root root 65536 Mar 5 19:38 reference_perf
36 -r--r--r-- 1 root root 65536 Mar 5 19:38 wraparound_time
35 37
36* highest_perf : Highest performance of this processor (abstract scale). 38* highest_perf : Highest performance of this processor (abstract scale).
37* nominal_perf : Highest sustained performance of this processor (abstract scale). 39* nominal_perf : Highest sustained performance of this processor
40 (abstract scale).
38* lowest_nonlinear_perf : Lowest performance of this processor with nonlinear 41* lowest_nonlinear_perf : Lowest performance of this processor with nonlinear
39 power savings (abstract scale). 42 power savings (abstract scale).
40* lowest_perf : Lowest performance of this processor (abstract scale). 43* lowest_perf : Lowest performance of this processor (abstract scale).
@@ -48,22 +51,26 @@ total 0
48* feedback_ctrs : Includes both Reference and delivered performance counter. 51* feedback_ctrs : Includes both Reference and delivered performance counter.
49 Reference counter ticks up proportional to processor's reference performance. 52 Reference counter ticks up proportional to processor's reference performance.
50 Delivered counter ticks up proportional to processor's delivered performance. 53 Delivered counter ticks up proportional to processor's delivered performance.
51* wraparound_time: Minimum time for the feedback counters to wraparound (seconds). 54* wraparound_time: Minimum time for the feedback counters to wraparound
55 (seconds).
52* reference_perf : Performance level at which reference performance counter 56* reference_perf : Performance level at which reference performance counter
53 accumulates (abstract scale). 57 accumulates (abstract scale).
54 58
55--------------------------------------------------------------------------------
56 59
57 Computing Average Delivered Performance 60Computing Average Delivered Performance
61=======================================
62
63Below describes the steps to compute the average performance delivered by
64taking two different snapshots of feedback counters at time T1 and T2.
65
66 T1: Read feedback_ctrs as fbc_t1
67 Wait or run some workload
58 68
59Below describes the steps to compute the average performance delivered by taking 69 T2: Read feedback_ctrs as fbc_t2
60two different snapshots of feedback counters at time T1 and T2.
61 70
62T1: Read feedback_ctrs as fbc_t1 71::
63 Wait or run some workload
64T2: Read feedback_ctrs as fbc_t2
65 72
66delivered_counter_delta = fbc_t2[del] - fbc_t1[del] 73 delivered_counter_delta = fbc_t2[del] - fbc_t1[del]
67reference_counter_delta = fbc_t2[ref] - fbc_t1[ref] 74 reference_counter_delta = fbc_t2[ref] - fbc_t1[ref]
68 75
69delivered_perf = (refernce_perf x delivered_counter_delta) / reference_counter_delta 76 delivered_perf = (refernce_perf x delivered_counter_delta) / reference_counter_delta
diff --git a/Documentation/admin-guide/acpi/index.rst b/Documentation/admin-guide/acpi/index.rst
index d68e9914c5ff..9049a7b9f065 100644
--- a/Documentation/admin-guide/acpi/index.rst
+++ b/Documentation/admin-guide/acpi/index.rst
@@ -10,3 +10,4 @@ the Linux ACPI support.
10 10
11 initrd_table_override 11 initrd_table_override
12 dsdt-override 12 dsdt-override
13 cppc_sysfs