Search nodes are single-purpose components of large Web search engines and their efficient implementation is critical to sustain thousands of queries per second and guarantee individual query response times within a fraction of a second. Current technology trends indicate that search nodes ought to be implemented as multithreaded multi-core systems. The straightforward solution that system designers can apply in this case is simply to follow standard practice by deploying one asynchronous

more »

... per active query in the node and attaching each thread to a different core. Each concurrent thread is responsible for sequentially processing a single query at a time. The only potential source of read/write conflicts among threads are the accesses to the different application caches present in the search node. However, new Web applications pose much more demanding requirements in terms of read/write conflicts than recent past applications since now data updates must take place concurrently with query processing. Insisting on the same paradigm of concurrent threads now augmented with a transaction concurrency control protocol is a feasible solution. In this paper we propose a more efficient and much simpler solution which has the additional advantage of enabling a very efficient administration of application caches. We propose performing relaxed bulksynchronous parallelism at multi-core level.