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Identifier 000425806
Title Support for different service levels through transparent migration of pages in distributed memory systems
Alternative Title Υποστήριξη διαφορετικών επιπέδων υπηρεσιών μέσω διάφανης μετακίνησης σελίδων σε κατανεμημένα συστήματα μνήμης
Author Σκορδαλάκης, Εμμανουήλ Ε.
Thesis advisor Πρατικάκης, Πολύβιος
Reviewer Κατεβαίνης, Μανόλης
Μπίλας, Άγγελος
Abstract With the constant evolution of high performance applications, their memory requirement is rapidly increasing. As a result, the demand for more memory on computer nodes of large clusters running those applications, continuously rises. However, an individual computer node has limits in terms of memory capacity. Typically, by running several processes of different computational and memory requirements on a cluster, creates fluctuating workloads among the computer nodes. Hence, several nodes use most of their memory while others are left with unused memory which could potentially be exploited by nodes with a heavy memory workload. Consequently, the concept of remote memory management has become the subject for research by many organizations, which have implemented varying techniques for reading and writing data on remote memory. Although using remote memory practically increases the total available memory of a computer node, accessing data remotely, can critically minimize performance due to the data travelling through the network interconnection of the cluster. Furthermore, software APIs that are implemented to give processes access to remote memory, primarily can be complex, and secondly the responsibility for remote memory allocation and fair remote memory sharing among processes, is assigned to processes themselves, which can be quite complicated, especially when many processes are running simultaneously on the same computer node. In this MSc thesis, we present the Page Migration System(PMS), which monitors main memory usage of the computer nodes on a cluster, and moves infrequently accessed data of a process from the memory of a computer node with heavy memory workload, to the unused memory of a remote computer node of the same cluster node with a lighter memory workload. The key features of the PMS is that it transparently moves LRU pages of processes to remote memory while using a fairness algorithm when choosing memory pages among many processes running on the same computer node. What's more, remote memory is mapped on the local node, allowing the OS to cache remote data. To be precise, a read and/or write on remote memory happens when we get a cache miss. Cacheability offers better performance when there are less misses, by reducing network transfers. Finally the system is able to return memory pages locally if the overall node memory usage drops, or if the access frequency of those memory pages increases. We evaluate the PMS using several benchmarks that stress the CPU in terms of memory access. We use benchmarks that perform raw serial access on arrays of around a Gigabyte in size and thus cause cache eviction frequently, essentially moving more data through the network. That way we can measure the performance drop of a process due to memory access in the worst case scenario. We also run cache blocking benchmarks that exploit temporal locality, and we show that we get a better performance that way by reducing operations on remote memory. Finally we observe the behaviour and performance on real HPC applications using the PMS.
Language English
Subject Clusters
Remote memory
Απομακρυσμένη μνήμη
Issue date 2019-11-22
Collection   Faculty/Department--Faculty of Sciences and Engineering--Department of Computer Science--Post-graduate theses
  Type of Work--Post-graduate theses
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