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1What: /sys/bus/event_source/devices/cpu.../rdpmc
2Date: November 2011
3KernelVersion: 3.10
4Contact: Linux kernel mailing list linux-kernel@vger.kernel.org
5Description: The /sys/bus/event_source/devices/cpu.../rdpmc attribute
6 is used to show/manage if rdpmc instruction can be
7 executed in user space. This attribute supports 3 numbers.
8 - rdpmc = 0
9 user space rdpmc is globally disabled for all PMU
10 counters.
11 - rdpmc = 1
12 user space rdpmc is globally enabled only in event mmap
13 ioctl called time window. If the mmap region is unmapped,
14 user space rdpmc is disabled again.
15 - rdpmc = 2
16 user space rdpmc is globally enabled for all PMU
17 counters.
18
19 In the Intel platforms supporting counter level's user
20 space rdpmc disable feature (CPUID.23H.EBX[2] = 1), the
21 meaning of 3 numbers is extended to
22 - rdpmc = 0
23 global user space rdpmc and counter level's user space
24 rdpmc of all counters are both disabled.
25 - rdpmc = 1
26 No changes on behavior of global user space rdpmc.
27 counter level's rdpmc of system-wide events is disabled
28 but counter level's rdpmc of non-system-wide events is
29 enabled.
30 - rdpmc = 2
31 global user space rdpmc and counter level's user space
32 rdpmc of all counters are both enabled unconditionally.
33
34 The default value of rdpmc is 1.
35
36 Please notice:
37 - global user space rdpmc's behavior would change
38 immediately along with the rdpmc value's change,
39 but the behavior of counter level's user space rdpmc
40 won't take effect immediately until the event is
41 reactivated or recreated.
42 - The rdpmc attribute is global, even for x86 hybrid
43 platforms. For example, changing cpu_core/rdpmc will
44 also change cpu_atom/rdpmc.