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author | Fenghua Yu <fenghua.yu@intel.com> | 2019-06-20 04:33:57 +0300 |
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committer | Thomas Gleixner <tglx@linutronix.de> | 2019-06-24 02:44:20 +0300 |
commit | bd9a0c97e53c3d7a56b2751179903ddc5da42683 (patch) | |
tree | 012e64f9704bf31a42ee489ca0b597527ab22619 /Documentation/ABI/testing/sysfs-devices-system-cpu | |
parent | ff4b353f2ef9dc8e396d7cb9572801e34a8c7374 (diff) | |
download | linux-bd9a0c97e53c3d7a56b2751179903ddc5da42683.tar.xz |
x86/umwait: Add sysfs interface to control umwait maximum time
IA32_UMWAIT_CONTROL[31:2] determines the maximum time in TSC-quanta
that processor can stay in C0.1 or C0.2. A zero value means no maximum
time.
Each instruction sets its own deadline in the instruction's implicit
input EDX:EAX value. The instruction wakes up if the time-stamp counter
reaches or exceeds the specified deadline, or the umwait maximum time
expires, or a store happens in the monitored address range in umwait.
The administrator can write an unsigned 32-bit number to
/sys/devices/system/cpu/umwait_control/max_time to change the default
value. Note that a value of zero means there is no limit. The lower two
bits of the value must be zero.
[ tglx: Simplify the write function. Massage changelog ]
Signed-off-by: Fenghua Yu <fenghua.yu@intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Ashok Raj <ashok.raj@intel.com>
Reviewed-by: Tony Luck <tony.luck@intel.com>
Cc: "Borislav Petkov" <bp@alien8.de>
Cc: "H Peter Anvin" <hpa@zytor.com>
Cc: "Andy Lutomirski" <luto@kernel.org>
Cc: "Peter Zijlstra" <peterz@infradead.org>
Cc: "Ravi V Shankar" <ravi.v.shankar@intel.com>
Link: https://lkml.kernel.org/r/1560994438-235698-5-git-send-email-fenghua.yu@intel.com
Diffstat (limited to 'Documentation/ABI/testing/sysfs-devices-system-cpu')
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