App-aware Swap Resource Allocation for Enhancing User-perceived Latency on Mobile Devices

For smart mobile devices such as smartphones, daily usage involves a large set of apps and frequent app switching. App-switching latency is highly perceptible to users and is heavily subject to swap efficiency. Hybrid swapping, which combines compressed ramdisk (zRAM) and flash storage, is becoming increasingly popular in modern smartphones. However, existing approaches allocate these heterogeneous swap resources without app-level differentiation, resulting in suboptimal swap efficiency. To address this issue, we propose an integrated approach to hybrid swap based on app-level differentiation, involving three key strategies: app-aware page admission , which prioritizes hot-app pages for zRAM while directing cold-app pages to flash swap; app-aware page migration , which applies per-app criteria to identify and migrate dormant pages from zRAM to flash swap; and app-aware flash swap , which exploits swap space isolation and enhanced prefetching to mitigate flash-induced latency during app switching. Swap space isolation preserves the correlation of sequentially evicted pages from the same app, while our new prefetcher exploits dual correlations in eviction sequences and virtual addresses through per-app prefetch windows. Experimental results show that our approach reduces app-switching latency by up to 63% compared with existing methods.