In modern server CPUs, last-level cache (LLC) is a critical hardware resource that exerts significant influence on the performance of the workloads, and how to manage LLC is a key to the performance isolation and QoS in the cloud with multi-tenancy. In this paper, we argue that besides CPU cores, high-speed network I/O is also important for LLC management. This is because of an Intel architectural innovation -- Data Direct I/O (DDIO) -- that directly injects the inbound I/O traffic to (part of) the LLC instead of the main memory. We summarize two problems caused by DDIO and show that (1) the default DDIO configuration may not always achieve optimal performance, (2) DDIO can decrease the performance of non-I/O workloads which share LLC with it by as high as 32%. We then present IOCA, the first LLC management mechanism for network-centric platforms that treats the I/O as the first-class citizen. IOCA monitors and analyzes the performance of the cores, LLC, and DDIO using CPU's hardware performance counters, and adaptively adjusts the number of LLC ways for DDIO or the tenants that demand more LLC capacity. In addition, IOCA dynamically chooses the tenants that share its LLC resource with DDIO, to minimize the performance interference by both the tenants and the I/O. Our experiments with multiple microbenchmarks and real-world applications in two major end-host network models demonstrate that IOCA can effectively reduce the performance degradation caused by DDIO, with minimal overhead.

中文翻译：

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IOCA：面向以网络为中心的多租户平台的高速 I/O 感知 LLC 管理

在现代服务器 CPU 中，最后一级缓存（LLC）是一种关键的硬件资源，对工作负载的性能产生重大影响，如何管理 LLC 是多租户云中性能隔离和 QoS 的关键。在本文中，我们认为除了 CPU 内核之外，高速网络 I/O 对于 LLC 管理也很重要。这是因为英特尔架构创新——数据直接 I/O (DDIO)——直接将入站 I/O 流量注入（部分）LLC 而不是主内存。我们总结了 DDIO 引起的两个问题，并表明 (1) 默认的 DDIO 配置可能无法始终达到最佳性能，(2) DDIO 可以将与其共享 LLC 的非 I/O 工作负载的性能降低高达 32% . 然后我们介绍 IOCA，以网络为中心的平台的第一个 LLC 管理机制，将 I/O 视为一等公民。IOCA 使用 CPU 的硬件性能计数器监控和分析内核、LLC 和 DDIO 的性能，并为 DDIO 或需要更多 LLC 容量的租户自适应地调整 LLC 方式的数量。此外，IOCA 动态选择与 DDIO 共享其 LLC 资源的租户，以最大限度地减少租户和 I/O 对性能的干扰。我们在两个主要终端主机网络模型中对多个微基准测试和实际应用进行的实验表明，IOCA 可以以最小的开销有效减少 DDIO 导致的性能下降。s 硬件性能计数器，并为 DDIO 或需要更多 LLC 容量的租户自适应调整 LLC 方式的数量。此外，IOCA 动态选择与 DDIO 共享其 LLC 资源的租户，以最大限度地减少租户和 I/O 对性能的干扰。我们在两个主要终端主机网络模型中对多个微基准测试和实际应用进行的实验表明，IOCA 可以以最小的开销有效减少 DDIO 导致的性能下降。s 硬件性能计数器，并为 DDIO 或需要更多 LLC 容量的租户自适应调整 LLC 方式的数量。此外，IOCA 动态选择与 DDIO 共享其 LLC 资源的租户，以最大限度地减少租户和 I/O 对性能的干扰。我们在两个主要终端主机网络模型中对多个微基准测试和实际应用进行的实验表明，IOCA 可以以最小的开销有效减少 DDIO 导致的性能下降。