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authorVenkatesh Pallipadi <venkatesh.pallipadi@intel.com>2006-10-03 12:38:45 -0700
committerDave Jones <davej@redhat.com>2006-10-15 19:57:11 -0400
commitdfde5d62ed9b28b0bda676c16e8cb635df244ef2 (patch)
tree12c690189fcc7155389860beae554199456b7d3e /include/asm-x86_64
parenta6f6e6e6ab464c9d1dff66570b78be2f66d8ba3d (diff)
[CPUFREQ][8/8] acpi-cpufreq: Add support for freq feedback from hardware
Enable ondemand governor and acpi-cpufreq to use IA32_APERF and IA32_MPERF MSR to get active frequency feedback for the last sampling interval. This will make ondemand take right frequency decisions when hardware coordination of frequency is going on. Without APERF/MPERF, ondemand can take wrong decision at times due to underlying hardware coordination or TM2. Example: * CPU 0 and CPU 1 are hardware cooridnated. * CPU 1 running at highest frequency. * CPU 0 was running at highest freq. Now ondemand reduces it to some intermediate frequency based on utilization. * Due to underlying hardware coordination with other CPU 1, CPU 0 continues to run at highest frequency (as long as other CPU is at highest). * When ondemand samples CPU 0 again next time, without actual frequency feedback from APERF/MPERF, it will think that previous frequency change was successful and can go to wrong target frequency. This is because it thinks that utilization it has got this sampling interval is when running at intermediate frequency, rather than actual highest frequency. More information about IA32_APERF IA32_MPERF MSR: Refer to IA-32 IntelĀ® Architecture Software Developer's Manual at http://developer.intel.com Signed-off-by: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com> Signed-off-by: Dave Jones <davej@redhat.com>
Diffstat (limited to 'include/asm-x86_64')
-rw-r--r--include/asm-x86_64/msr.h3
1 files changed, 3 insertions, 0 deletions
diff --git a/include/asm-x86_64/msr.h b/include/asm-x86_64/msr.h
index 37e194169fa..e6158228873 100644
--- a/include/asm-x86_64/msr.h
+++ b/include/asm-x86_64/msr.h
@@ -307,6 +307,9 @@ static inline unsigned int cpuid_edx(unsigned int op)
#define MSR_IA32_PERF_STATUS 0x198
#define MSR_IA32_PERF_CTL 0x199
+#define MSR_IA32_MPERF 0xE7
+#define MSR_IA32_APERF 0xE8
+
#define MSR_IA32_THERM_CONTROL 0x19a
#define MSR_IA32_THERM_INTERRUPT 0x19b
#define MSR_IA32_THERM_STATUS 0x19c