tailieunhanh - Multiprocessor Support for Event-Driven Programs

Such an approach, however, is fraught with security risks: without proper protection in place, one’s sensitive information can be exposed to unintended par- ties on the same system. This threat is often dealt with by an access controlmechanism that confines each user’s activities to her compartment. As an example, programs running in a user’s account are typically not allowed to touch the data in another account without the permission of the owner of that account. The problem is that dif- ferent users do need to interact with each other, and they usually expect this to happen in a convenient way. As a result, most multi-user systems tend to trade security and privacy. | Multiprocessor Support for Event-Driven Programs Nickolai Zeldovich Alexander Yip Frank Dabek Robert T. Morris David Mazieresy Frans Kaashoek nickolai@ yipal fdabek rtm kaashoekg@ dm@ MIT Laboratory for Computer Science 200 Technology Square Cambridge MA 02139 Abstract This paper presents a new asynchronous programming library libasync-smp that allows event-driven applications to take advantage of multiprocessors by running code for event handlers in parallel. To control the concurrency between events the programmer can specify a color for each event events with the same color the default case are handled serially events with different colors can be handled in parallel. The programmer can incrementally expose parallelism in existing event-driven applications by assigning different colors to computationally-intensive events that do not share mutable state. An evaluation of libasync-smp demonstrates that applications achieve multiprocessor speedup with little programming effort. As an example parallelizing the cryptography in the SFS file server required about 90 lines of changed code in two modules out of a total of about 12 000 lines. Multiple clients were able to read large cached files from the libasync-smp SFS server running on a 4-CPU machine times as fast as from an unmodified uniprocessor SFS server on one CPU. Applications without computationally intensive tasks also benefit an event-driven Web server achieves speedup on four CPUs with multiple clients reading small cached files. 1 Introduction To obtain high performance servers must overlap computation with I O. Programs typically achieve this overlap using threads or events. Threaded programs typically process each request in a separate thread when one thread blocks waiting for I O other threads can run. Threads provide an intuitive programming model and can take advantage of multiprocessors however they Stanford University y New York University require .

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