Reducing the power consumption of applications has become one of the key challenges in high-performance computing. Recent processor architectures differentiate processor core frequency from its uncore frequency. As a consequence, in addition to tuning processor core frequency with Dynamic Voltage and Frequency Scaling (DVFS), power consumption can also be controlled through Uncore Frequency Scaling (UFS).This paper studies how the uncore frequency can be used as a leverage to improve power consumption. We propose DUF, a daemon process that dynamically adapts the uncore frequency to reduce an application power consumption with a user-defined limit on performance degradation.The evaluation of DUF on three different architectures shows that with no performance degradation (less than 0.6 %), DUF can reduce socket power consumption by 7.94 %. We also show that DUF is able to reduce the total energy consumption by up to 18.20 %.
Understanding the performance of a multi-threaded application is difficult. The threads interfere when they access the same shared resource, which slows down their execution. Unfortunately, current profiling tools report the hardware components or the synchronization primitives that saturate, but they cannot tell if the saturation is the cause of a performance bottleneck. In this paper, we propose a holistic metric able to pinpoint the blocks of code that suffer interference the most, regardless of the interference cause. Our metric uses performance variation as a universal indicator of interference problems. With an evaluation of 27 applications we show that our metric can identify interference problems caused by 6 different kinds of interference in 9 applications. We are able to easily remove 7 of the bottlenecks, which leads to a performance improvement of up to 9 times.
This paper introduces NVCACHE, an approach that uses a non-volatile main memory (NVMM) as a write cache to improve the write performance of legacy applications. We compare NVCACHE against file systems tailored for NVMM (Ext4-DAX and NOVA) and with I/O-heavy applications (SQLite, RocksDB). Our evaluation shows that NVCACHE reaches the performance level of the existing state-of-the-art systems for NVMM, but without their limitations: NVCACHE does not limit the size of the stored data to the size of the NVMM, and works transparently with unmodified legacy applications, providing additional persistence guarantees even when their source code is not available.
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