Understanding, modelling and improving the performance of web applications in multi-core virtualised environments

As the computing industry enters the Cloud era, multicore architectures and virtualisation technologies are replacing traditional IT infrastructures. However, the complex rela-tionship between applications and system resources in multi-core virtualised environments is not well understood. Work-loads such as web services and on-line financial applications have the requirement of high performance but benchmark analysis suggests that these applications do not optimally benefit from a higher number of cores. In this paper, we try to understand the scalability be-haviour of network/CPU intensive applications running on multicore architectures. We begin by benchmarking the Pet-store web application, noting the systematic imbalance that arises with respect to per-core workload. Having identi-fied the reason for this phenomenon, we propose a queue-ing model which, when appropriately parametrised, reflects the trend in our benchmark results for up to 8 cores. Key to our approach is providing a fine-grained model which in-corporates the idiosyncrasies of the operating system and the multiple CPU cores. Analysis of the model suggests a straightforward way to mitigate the observed bottleneck, which can be practically realised by the deployment of mul-tiple virtual NICs within our VM. Next we make blind pre-dictions to forecast performance with multiple virtual NICs. The validation results show that the model is able to pre-dict the expected performance with relative errors ranging between 8 and 26%