| What: /sys/bus/event_source/devices/cpu.../rdpmc |
| Date: November 2011 |
| KernelVersion: 3.10 |
| Contact: Linux kernel mailing list linux-kernel@vger.kernel.org |
| Description: The /sys/bus/event_source/devices/cpu.../rdpmc attribute |
| is used to show/manage if rdpmc instruction can be |
| executed in user space. This attribute supports 3 numbers. |
| - rdpmc = 0 |
| user space rdpmc is globally disabled for all PMU |
| counters. |
| - rdpmc = 1 |
| user space rdpmc is globally enabled only in event mmap |
| ioctl called time window. If the mmap region is unmapped, |
| user space rdpmc is disabled again. |
| - rdpmc = 2 |
| user space rdpmc is globally enabled for all PMU |
| counters. |
| |
| In the Intel platforms supporting counter level's user |
| space rdpmc disable feature (CPUID.23H.EBX[2] = 1), the |
| meaning of 3 numbers is extended to |
| - rdpmc = 0 |
| global user space rdpmc and counter level's user space |
| rdpmc of all counters are both disabled. |
| - rdpmc = 1 |
| No changes on behavior of global user space rdpmc. |
| counter level's rdpmc of system-wide events is disabled |
| but counter level's rdpmc of non-system-wide events is |
| enabled. |
| - rdpmc = 2 |
| global user space rdpmc and counter level's user space |
| rdpmc of all counters are both enabled unconditionally. |
| |
| The default value of rdpmc is 1. |
| |
| Please notice: |
| - global user space rdpmc's behavior would change |
| immediately along with the rdpmc value's change, |
| but the behavior of counter level's user space rdpmc |
| won't take effect immediately until the event is |
| reactivated or recreated. |
| - The rdpmc attribute is global, even for x86 hybrid |
| platforms. For example, changing cpu_core/rdpmc will |
| also change cpu_atom/rdpmc. |
