1 Intel hybrid support
2 --------------------
3 Support for Intel hybrid events within perf tools.
4
5 For some Intel platforms, such as AlderLake, which is hybrid platform and
6 it consists of atom cpu and core cpu. Each cpu has dedicated event list.
7 Part of events are available on core cpu, part of events are available
8 on atom cpu and even part of events are available on both.
9
10 Kernel exports two new cpu pmus via sysfs:
11 /sys/devices/cpu_core
12 /sys/devices/cpu_atom
13
14 The 'cpus' files are created under the directories. For example,
15
16 cat /sys/devices/cpu_core/cpus
17 0-15
18
19 cat /sys/devices/cpu_atom/cpus
20 16-23
21
22 It indicates cpu0-cpu15 are core cpus and cpu16-cpu23 are atom cpus.
23
24 As before, use perf-list to list the symbolic event.
25
26 perf list
27
28 inst_retired.any
29 [Fixed Counter: Counts the number of instructions retired. Unit: cpu_atom]
30 inst_retired.any
31 [Number of instructions retired. Fixed Counter - architectural event. Unit: cpu_core]
32
33 The 'Unit: xxx' is added to brief description to indicate which pmu
34 the event is belong to. Same event name but with different pmu can
35 be supported.
36
37 Enable hybrid event with a specific pmu
38
39 To enable a core only event or atom only event, following syntax is supported:
40
41 cpu_core/<event name>/
42 or
43 cpu_atom/<event name>/
44
45 For example, count the 'cycles' event on core cpus.
46
47 perf stat -e cpu_core/cycles/
48
49 Create two events for one hardware event automatically
50
51 When creating one event and the event is available on both atom and core,
52 two events are created automatically. One is for atom, the other is for
53 core. Most of hardware events and cache events are available on both
54 cpu_core and cpu_atom.
55
56 For hardware events, they have pre-defined configs (e.g. 0 for cycles).
57 But on hybrid platform, kernel needs to know where the event comes from
58 (from atom or from core). The original perf event type PERF_TYPE_HARDWARE
59 can't carry pmu information. So now this type is extended to be PMU aware
60 type. The PMU type ID is stored at attr.config[63:32].
61
62 PMU type ID is retrieved from sysfs.
63 /sys/devices/cpu_atom/type
64 /sys/devices/cpu_core/type
65
66 The new attr.config layout for PERF_TYPE_HARDWARE:
67
68 PERF_TYPE_HARDWARE: 0xEEEEEEEE000000AA
69 AA: hardware event ID
70 EEEEEEEE: PMU type ID
71
72 Cache event is similar. The type PERF_TYPE_HW_CACHE is extended to be
73 PMU aware type. The PMU type ID is stored at attr.config[63:32].
74
75 The new attr.config layout for PERF_TYPE_HW_CACHE:
76
77 PERF_TYPE_HW_CACHE: 0xEEEEEEEE00DDCCBB
78 BB: hardware cache ID
79 CC: hardware cache op ID
80 DD: hardware cache op result ID
81 EEEEEEEE: PMU type ID
82
83 When enabling a hardware event without specified pmu, such as,
84 perf stat -e cycles -a (use system-wide in this example), two events
85 are created automatically.
86
87 ------------------------------------------------------------
88 perf_event_attr:
89 size 120
90 config 0x400000000
91 sample_type IDENTIFIER
92 read_format TOTAL_TIME_ENABLED|TOTAL_TIME_RUNNING
93 disabled 1
94 inherit 1
95 exclude_guest 1
96 ------------------------------------------------------------
97
98 and
99
100 ------------------------------------------------------------
101 perf_event_attr:
102 size 120
103 config 0x800000000
104 sample_type IDENTIFIER
105 read_format TOTAL_TIME_ENABLED|TOTAL_TIME_RUNNING
106 disabled 1
107 inherit 1
108 exclude_guest 1
109 ------------------------------------------------------------
110
111 type 0 is PERF_TYPE_HARDWARE.
112 0x4 in 0x400000000 indicates it's cpu_core pmu.
113 0x8 in 0x800000000 indicates it's cpu_atom pmu (atom pmu type id is random).
114
115 The kernel creates 'cycles' (0x400000000) on cpu0-cpu15 (core cpus),
116 and create 'cycles' (0x800000000) on cpu16-cpu23 (atom cpus).
117
118 For perf-stat result, it displays two events:
119
120 Performance counter stats for 'system wide':
121
122 6,744,979 cpu_core/cycles/
123 1,965,552 cpu_atom/cycles/
124
125 The first 'cycles' is core event, the second 'cycles' is atom event.
126
127 Thread mode example:
128
129 perf-stat reports the scaled counts for hybrid event and with a percentage
130 displayed. The percentage is the event's running time/enabling time.
131
132 One example, 'triad_loop' runs on cpu16 (atom core), while we can see the
133 scaled value for core cycles is 160,444,092 and the percentage is 0.47%.
134
135 perf stat -e cycles \-- taskset -c 16 ./triad_loop
136
137 As previous, two events are created.
138
139 ------------------------------------------------------------
140 perf_event_attr:
141 size 120
142 config 0x400000000
143 sample_type IDENTIFIER
144 read_format TOTAL_TIME_ENABLED|TOTAL_TIME_RUNNING
145 disabled 1
146 inherit 1
147 enable_on_exec 1
148 exclude_guest 1
149 ------------------------------------------------------------
150
151 and
152
153 ------------------------------------------------------------
154 perf_event_attr:
155 size 120
156 config 0x800000000
157 sample_type IDENTIFIER
158 read_format TOTAL_TIME_ENABLED|TOTAL_TIME_RUNNING
159 disabled 1
160 inherit 1
161 enable_on_exec 1
162 exclude_guest 1
163 ------------------------------------------------------------
164
165 Performance counter stats for 'taskset -c 16 ./triad_loop':
166
167 233,066,666 cpu_core/cycles/ (0.43%)
168 604,097,080 cpu_atom/cycles/ (99.57%)
169
170 perf-record:
171
172 If there is no '-e' specified in perf record, on hybrid platform,
173 it creates two default 'cycles' and adds them to event list. One
174 is for core, the other is for atom.
175
176 perf-stat:
177
178 If there is no '-e' specified in perf stat, on hybrid platform,
179 besides of software events, following events are created and
180 added to event list in order.
181
182 cpu_core/cycles/,
183 cpu_atom/cycles/,
184 cpu_core/instructions/,
185 cpu_atom/instructions/,
186 cpu_core/branches/,
187 cpu_atom/branches/,
188 cpu_core/branch-misses/,
189 cpu_atom/branch-misses/
190
191 Of course, both perf-stat and perf-record support to enable
192 hybrid event with a specific pmu.
193
194 e.g.
195 perf stat -e cpu_core/cycles/
196 perf stat -e cpu_atom/cycles/
197 perf stat -e cpu_core/r1a/
198 perf stat -e cpu_atom/L1-icache-loads/
199 perf stat -e cpu_core/cycles/,cpu_atom/instructions/
200 perf stat -e '{cpu_core/cycles/,cpu_core/instructions/}'
201
202 But '{cpu_core/cycles/,cpu_atom/instructions/}' will return
203 warning and disable grouping, because the pmus in group are
204 not matched (cpu_core vs. cpu_atom).
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