Intel Uncore Linux Driver Prepares ELC "Efficiency Latency Control" Feature
A set of three patches were posted a few minutes ago to the Linux x86 platform driver mailing list for introducing this Efficiency Latency Control feature to the Intel TPMI uncore driver. With the new patches, the documentation being added explains the Intel ELC feature as:
Efficiency vs. Latency Tradeoff
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In the realm of high-performance computing, particularly with Xeon processors, managing uncore frequency is an important aspect of system optimization. Traditionally, the uncore frequency is ramped up rapidly in high load scenarios. While this strategy achieves low latency, which is crucial for time-sensitive computations, it does not necessarily yield the best performance per watt, —a key metric for energy efficiency and operational cost savings.
The Efficiency vs. Latency Control (ELC) feature allows user to influence the uncore frequency scaling algorithm. Hardware monitors the average CPU utilization across all cores at regular intervals. If the average CPU utilization is below a user defined threshold (elc_low_threshold_percent), the user defined uncore frequency floor frequency will be used (elc_floor_freq_khz), minimizing latency. Similarly in high load scenario where the CPU utilization goes above the high threshold value (elc_high_threshold_percent) instead of jumping to maximum uncore frequency, uncore frequency is increased in 100MHz steps until the power limit is reached.
The Intel Efficiency Latency Control for the uncore can be controlled with these patches via the new sysfs interfaces for fine-tuning newer Intel SoCs. The patches do not indicate what "newer" generations of Intel SoCs offer configurable ELC support.
The Intel ELC Linux patches for now can be found on the platform-driver-x86 mailing list while undergoing code review.
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