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authorSrinivas Pandruvada <srinivas.pandruvada@linux.intel.com>2017-07-13 15:03:51 -0700
committerRafael J. Wysocki <rafael.j.wysocki@intel.com>2017-07-14 03:01:28 +0200
commit6e34e1f23d780978da65968327cbba6d7013a73f (patch)
treee11a032791c000465112450a672b7919da5a9ec0 /lib/iommu-common.c
parentd4436c0dba8d4d780588179a2e192a867d266a10 (diff)
cpufreq: intel_pstate: Correct the busy calculation for KNL
The busy percent calculated for the Knights Landing (KNL) platform is 1024 times smaller than the correct busy value. This causes performance to get stuck at the lowest ratio. The scaling algorithm used for KNL is performance-based, but it still looks at the CPU load to set the scaled busy factor to 0 when the load is less than 1 percent. In this case, since the computed load is 1024x smaller than it should be, the scaled busy factor will always be 0, irrespective of CPU business. This needs a fix similar to the turbostat one in commit b2b34dfe4d9a (tools/power turbostat: KNL workaround for %Busy and Avg_MHz). For this reason, add one more callback to processor-specific callbacks to specify an MPERF multiplier represented by a number of bit positions to shift the value of that register to the left to copmensate for its rate difference with respect to the TSC. This shift value is used during CPU busy calculations. Fixes: ffb810563c (intel_pstate: Avoid getting stuck in high P-states when idle) Reported-and-tested-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com> Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com> Cc: 4.6+ <stable@vger.kernel.org> # 4.6+ [ rjw: Changelog ] Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
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