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Documentation: intel_pstate: Clarify coordination of P-State limits

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Explain influence of per-core P-states and hyper threading on the
effective performance.

Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
This commit is contained in:
Srinivas Pandruvada 2018-11-16 14:24:20 -08:00 committed by Rafael J. Wysocki
parent af3b7379e2
commit 60935c17e2
1 changed files with 9 additions and 1 deletions
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Documentation/admin-guide/pm/intel_pstate.rst
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@ -495,7 +495,15 @@ on the following rules, regardless of the current operation mode of the driver:
2. Each individual CPU is affected by its own per-policy limits (that is, it
cannot be requested to run faster than its own per-policy maximum and it
cannot be requested to run slower than its own per-policy minimum).
cannot be requested to run slower than its own per-policy minimum). The
effective performance depends on whether the platform supports per core
P-states, hyper-threading is enabled and on current performance requests
from other CPUs. When platform doesn't support per core P-states, the
effective performance can be more than the policy limits set on a CPU, if
other CPUs are requesting higher performance at that moment. Even with per
core P-states support, when hyper-threading is enabled, if the sibling CPU
is requesting higher performance, the other siblings will get higher
performance than their policy limits.
3. The global and per-policy limits can be set independently.