Computer supported collaborative writing in an early learning classroom

Abstract This paper describes a collaborative experiment in an early learners' classroom, equipped with special software and hardware to support the acquisition of initial reading and writing skills. This 'Computer-integrated Classroom' originated from the EU project NIMIS. Here, a new method to teach 'reading through writing' is supported by a specific software tool (T³) in the general framework of the classroom environment. Particularly, a collaborative writing task facilitated by a shared workspace system has been evaluated with a group of first graders using the T³ application. The speciality of this experiment lies in the study of domain-specific collaboration in a rich real world learning setting.  

一种基于小数据同步写的回写I/O调度器

小数据同步写普遍存在于的各种计算机环境中，并且可以由计算机系统的不同层次软件产生，从底层操作系统一直到上层应用软件都可以生成小数据同步写请求.然而，操作系统的文件系统是以块作为最小逻辑可寻址单位，小数据写将会导致严重的写放大问题，使得系统的I/O性能大幅降低.为了解决上述问题，我们提出了一种新的I/O调度器，并将它取名为“Hitchhike”.该调度器可以识别小数据写，并通过对其他数据块中的数据进行压缩，，将小数据嵌入到压缩出来的空间中，从而将小数据和该数据块一起写入到磁盘上，以异步回写的方式完成小数据的同步写，不仅有效缓解了磁盘的写放大问题，也大大提高了小数据同步写的效率.我们基于Linux中Deadline调度器实现了Hitchhike原型系统，并利用Filebench基准测试来测试调度器在吞吐量、I/O延迟等方面的性能.通过和传统I/O调度器的性能进行比较，我们可以发现Hitchhike调度器能够显著的提高小数据同步写性能高达48.6%.