We examine status updating systems in which time-stamped status updates are stored/written in shared-memory. Specifically, we compare Read-Copy-Update (RCU) and Readers-Writer lock (RWL) as shared-memory synchronization primitives on the update freshness. To demonstrate the tension between readers and writers accessing shared-memory, we consider a network scenario with a pair of coupled updating processes. Location updates of a mobile terminal are written to a shared-memory Forwarder Information Base (FIB) at a network forwarder. An application server sends ``app updates'' to the mobile terminal via the forwarder. Arriving app updates at forwarder are addressed (by reading the FIB) and forwarded to the mobile terminal. If a FIB read returns an outdated address, the misaddressed app update is lost in transit. We redesign these reader and writer processes using preemption mechanisms that improve the timeliness of updates. We present a Stochastic Hybrid System (SHS) framework to analyze location and app update age processes and show how these two age processes are coupled through synchronization primitives. Our analysis shows that using a lock-based primitive (RWL) can serve fresher app updates to the mobile terminal at higher location update rates while lock-less (RCU) mechanism favors timely delivery of app updates at lower location update rates.

翻译：我们研究了共享内存中时间戳状态更新的存储/写入系统。具体来说，我们比较了读-复制-更新（RCU）和读写锁（RWL）这两种共享内存同步原语对更新新鲜度的影响。为展示读写进程访问共享内存时的冲突，我们考虑了一个包含耦合更新进程对的网络场景。移动终端的位置更新被写入网络转发器的共享内存转发信息库（FIB）。应用服务器通过转发器向移动终端发送“应用更新”。到达转发器的应用更新通过读取FIB获取地址，随后转发至移动终端。若FIB读取返回了过期地址，则寻址错误的应用更新会在传输中丢失。我们利用抢占机制重新设计了这些读写进程，以提升更新的时效性。我们提出了一种随机混合系统（SHS）框架，用于分析位置更新与应用更新的年龄过程，并展示这两个年龄过程如何通过同步原语相互耦合。分析表明，基于锁的原语（RWL）在较高位置更新率下能为移动终端提供更新鲜的应用更新，而无锁机制（RCU）则在较低位置更新率下更有利于应用更新的及时投递。