論文閱讀: Maintaining Application Context of Smartphones by Selectively Supporting Swap and Kill

Maintaining Application Context of Smartphones by Selectively Supporting Swap and Kill
JISUN KIM AND HYOKYUNG BAHN , (Member, IEEE)

與傳統的作業系統不同，Android OS 在Low memory的時候會根據oom_score將application kill來釋放Free page，這篇論文提出將部分的application以swap取代kill (Pure Android用的是zram not swap)

1. Instead of killing a process, the context of an application can be backed up to swap storage, but smartphones do not accept it as swap incurs excessively heavy I/O traffic.
2. Proposes a selective swap scheme that classifies applications based on their context-saving characteristics and controls the number of processes involved in swap by monitoring system situations and application characteristics.

Summarized，因此論文這邊主要比較了Swap的好處以及Killbase的好處。

1. 早期Android沒有Swap的原因主要是Heavy Traffic I/O會影響Flash的壽命。但現在UFS以及QLC的出現讓存儲系統有大量的進展。
2. 然而，當與swap vs kill system進行比較時，當執行的應用程序數量變得非常多時，基於swap系統仍然會產生大量的I/O traffic。
3. 因此我們提出Selective Swap 主要是通過監控系統狀態和應用程序特性來控制SwapProcesses amount。

Linux and Android deal with Low memory status

Selective Swap Scheme

1. Some smartphone applications are developed to maintain their context by themselves, not needing the assitance for swap.
2. The number of applications executed by a single user is
   limited, and thus situations that we need to control the number
   of processes to be swapped rarely happen.