Publications

@inproceedings{9138912,
title = {HieraGen: Automated Generation of Concurrent, Hierarchical Cache Coherence Protocols},
author = {N Oswald and V Nagarajan and D J Sorin},
doi = {10.1109/ISCA45697.2020.00077},
year = {2020},
date = {2020-05-01},
booktitle = {2020 ACM/IEEE 47th Annual International Symposium on Computer Architecture (ISCA)},
pages = {888-899},
abstract = {We present HieraGen, a new tool for automatically generating hierarchical cache coherence protocols. HieraGen's inputs are the simple, atomic, stable state protocols for each level of the hierarchy. HieraGen's output is a highly concurrent hierarchical protocol, in the form of the finite state machines for all of the cache and directory controllers. HieraGen thus reduces the complexity that architects face, by offloading the challenging tasks of composing protocols and managing concurrency. Experiments show that HieraGen can automatically generate correct-by-construction MOESI family of hierarchical protocols with dozens of states and hundreds of transitions. We have verified all of the generated protocols for safety and deadlock freedom using a model checker.},
keywords = {},
pubstate = {published},
tppubtype = {inproceedings}
}

@inproceedings{10.1109/ISCA.2018.00030,
title = {Protogen: Automatically Generating Directory Cache Coherence Protocols from Atomic Specifications},
author = {Nicolai Oswald and Vijay Nagarajan and Daniel J Sorin},
url = {https://doi.org/10.1109/ISCA.2018.00030},
doi = {10.1109/ISCA.2018.00030},
isbn = {9781538659847},
year = {2018},
date = {2018-01-01},
booktitle = {Proceedings of the 45th Annual International Symposium on Computer Architecture},
pages = {247–260},
publisher = {IEEE Press},
address = {Los Angeles, California},
series = {ISCA '18},
abstract = {Designing directory cache coherence protocols is complicated because coherence transactions are not atomic in modern multicore processors. A coherence transaction comprises multiple messages, and these messages can interleave with other conflicting coherence transactions initiated by other cores. To overcome this architectural challenge, we present ProtoGen, an automated tool for taking the description of a directory protocol with atomic transactions (i.e., no concurrency) and generating the corresponding protocol for a multicore with non-atomic transactions. ProtoGen outputs the finite state machines for the cache and directory controllers, including all of the transient states that are possible with concurrent transactions. We have used ProtoGen to generate complete MSI, MESI, and MOSI protocols given their stable state protocol specifications. We have verified the generated protocols for safety and deadlock freedom using the Murϕ model checker. Our generated protocols are identical to or better than manually generated protocols, at times even discovering opportunities to reduce stalling.},
keywords = {},
pubstate = {published},
tppubtype = {inproceedings}
}

@inproceedings{10.1145/3190508.3190550,
title = {Scale-out CcNUMA: Exploiting Skew with Strongly Consistent Caching},
author = {Vasilis Gavrielatos and Antonios Katsarakis and Arpit Joshi and Nicolai Oswald and Boris Grot and Vijay Nagarajan},
url = {https://doi.org/10.1145/3190508.3190550},
doi = {10.1145/3190508.3190550},
isbn = {9781450355841},
year = {2018},
date = {2018-01-01},
booktitle = {Proceedings of the Thirteenth EuroSys Conference},
publisher = {Association for Computing Machinery},
address = {Porto, Portugal},
series = {EuroSys '18},
abstract = {Today's cloud based online services are underpinned by distributed key-value stores (KVS). Such KVS typically use a scale-out architecture, whereby the dataset is partitioned across a pool of servers, each holding a chunk of the dataset in memory and being responsible for serving queries against the chunk. One important performance bottleneck that a KVS design must address is the load imbalance caused by skewed popularity distributions. Despite recent work on skew mitigation, existing approaches offer only limited benefit for high-throughput in-memory KVS deployments.In this paper, we embrace popularity skew as a performance opportunity. Our insight is that aggressively caching popular items at all nodes of the KVS enables both load balance and high throughput - a combination that has eluded previous approaches. We introduce symmetric caching, wherein every server node is provisioned with a small cache that maintains the most popular objects in the dataset. To ensure consistency across the caches, we use high-throughput fully-distributed consistency protocols. A key result of this work is that strong consistency guarantees (per-key linearizability) need not compromise on performance. In a 9-node RDMA-based rack and with modest write ratios, our prototype design, dubbed ccKVS, achieves 2.2x the throughput of the state-of-the-art KVS while guaranteeing strong consistency.},
keywords = {},
pubstate = {published},
tppubtype = {inproceedings}
}