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Frequent Translation Lookaside Buffer (TLB) misses incur high performance and energy costs due to page walks required for fetching the corresponding address translations. Prefetching page table entries (PTEs) ahead of demand TLB accesses can mitigate the address translation performance bottleneck, but each prefetch requires traversing the page table, triggering additional accesses to the memory hierarchy. Therefore, TLB prefetching is a costly technique that may undermine performance when the prefetches are not accurate.In this paper we exploit the locality in the last level of the page table to reduce the cost and enhance the effectiveness of TLB prefetching by fetching cache-line adjacent PTEs "for free". We propose Sampling-Based Free TLB Prefetching (SBFP), a dynamic scheme that predicts the usefulness of these "free" PTEs and prefetches only the ones most likely to prevent TLB misses. We demonstrate that combining SBFP with novel and state-of-theart TLB prefetchers significantly improves miss coverage and reduces most memory accesses due to page walks.Moreover, we propose Agile TLB Prefetcher (ATP), a novel composite TLB prefetcher particularly designed to maximize the benefits of SBFP. ATP efficiently combines three low-cost TLB prefetchers and disables TLB prefetching for those execution phases that do not benefit from it. Unlike state-of-the-art TLB prefetchers that correlate patterns with only one feature (e.g., strides, PC, distances), ATP correlates patterns with multiple features and dynamically enables the most appropriate TLB prefetcher per TLB miss.To alleviate the address translation performance bottleneck, we propose a unified solution that combines ATP and SBFP. Across an extensive set of industrial workloads provided by Qualcomm, ATP coupled with SBFP improves geometric speedup by 16.2%, and eliminates on average 37% of the memory references due to page walks. Considering the SPEC CPU 2006 and SPEC CPU 2017 benchmark suites, ATP with SBFP increases geometric speedup by 11.1%, and eliminates page walk memory references by 26%. Applied to big data workloads (GAP suite, XSBench), ATP with SBFP yields a geometric speedup of 11.8% while reducing page walk memory references by 5%. Over the best state-of-the-art TLB prefetcher for each benchmark suite, ATP with SBFP achieves speedups of 8.7%, 3.4%, and 4.2% for the Qualcomm, SPEC, and GAP+XSBench workloads, respectively.

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The rich, complementary data provided by Sentinel-1 and Sentinel-2 satellite constellations host considerable potential to transform Earth observation (EO) applications. However, a substantial amount of effort and infrastructure is still required for the generation of analysis-ready data (ARD) from the low-level products provided by the European Space Agency (ESA). Here, a flexible Python framework able to generate a range of consistent ARD aligned with the ESA-recommended processing pipeline is detailed. Sentinel-1 Synthetic Aperture Radar (SAR) data are radiometrically calibrated, speckle-filtered and terrain-corrected, and Sentinel-2 multi-spectral data resampled in order to harmonise the spatial resolution between the two streams and to allow stacking with multiple scene classification masks. The global coverage and flexibility of the framework allows users to define a specific region of interest (ROI) and time window to create geo-referenced Sentinel-1 and Sentinel-2 images, or a combination of both with closest temporal alignment. The framework can be applied to any location and is user-centric and versatile in generating multi-modal and multi-temporal ARD. Finally, the framework handles automatically the inherent challenges in processing Sentinel data, such as boundary regions with missing values within Sentinel-1 and the filtering of Sentinel-2 scenes based on ROI cloud coverage.

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