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Without any dedicated hypervisor tricks, can't a typical L3 cache eviction algorithm also evict memory that is assigned to another core and currently residing i
by lend000 6y ago
Without any dedicated hypervisor tricks, can't a typical L3 cache eviction algorithm also evict memory that is assigned to another core and currently residing in its L2 or L1 cache? (Thereby flushing even the higher level caches if another core is really noisy.)
- nisten 6y agoI'm not entirely sure, it looks like for Skylake CPUs the L3 cache is no longer inclusive but instead acts as an extension of the per core L2 cache. https://www.anandtech.com/show/11550/the-intel-skylakex-review-core-i9-7900x-i7-7820x-and-i7-7800x-tested/4 https://www.anandtech.com/show/11550/the-intel-skylakex-revi... I remember a while ago reading about storing your encryption keys in L2 instead of ram and deliberate "abuse" of the L3 cache on VPS hosts however can't find that article and haven't kept up with the news on it. Given that the intel cpu patches have reduced CPU performance by ~15% ( again sorry don't have the exact source) I'd say there has been quite significant changes in cache management in the name of security.
- lend000 6y agoThanks for the info. It's a dilemma when allocating instances because I want the full per-core performance but I don't need a full socket's worth of cores, so I just have to hope my neighbors aren't running huge jobs all the time.