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Reducing AVX-Induced Frequency Variation With Core Specialization

Gottschlag, Mathias; Bellosa, Frank

Recent Intel server processors temporarily reduce their frequency
when many AVX2 or AVX-512 SIMD instructions are executed.
The frequency change is only reverted two milliseconds after the
system has stopped executing such instructions. Before this time,
any non-vectorized (and potentially unrelated) code which could
execute at higher frequencies is slowed down. The effect on overall
performance depends on the specificworkload and is hard to predict.
We describe a scenario where vectorizing one component with AVX-
512 instructions improves performance by 10% for one workload
and reduces performance by 10% for another workload.
If only some of the cores of a system execute such vectorized
code, the frequency effect is limited to those cores. We propose
a scheduling algorithm as well as a mechanism to intercept problematic
code sections so that threads executing vectorized code
are transparently migrated to a small subset of the cores. While
our work is still in progress, we describe a partial implementation
which is able to reduce the negative performance impact of AVX2
and AVX-512 instructions by over 70%.

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Postprint §
DOI: 10.5445/IR/1000120628
Veröffentlicht am 29.06.2020
Cover der Publikation
Zugehörige Institution(en) am KIT Institut für Technische Informatik (ITEC)
Publikationstyp Proceedingsbeitrag
Publikationsdatum 25.03.2019
Sprache Englisch
Identifikator KITopen-ID: 1000120628
Erschienen in The 9th Workshop on Systems for Multi-core and Heterogeneous Architectures
Veranstaltung Workshop on Systems for Multi-core and Heterogeneous Architectures (2019), Dresden, Deutschland, 25.02.2019 – 28.03.2019
Verlag Dresden, Germany
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