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I think you are either confusing virtual machines with containers, or using containers where any OS differences are transparently hidden by starting a VPS with

• jandrewrogers 5y ago
  There is a litany of ways in which syscalls behave differently when using containers that degrade performance for high-performance software relative to bare metal (or virtual machines, ironically). Many people have observed and tried to debug these issues. There might be a way to empirically make containers work correctly for this type of software but no one has been able to discover how, and not for lack of trying. No process serious about I/O performance uses the system kernel for I/O. Doing it in user space is integer factor higher throughput, hence why Linux has APIs to make this possible for software that needs it. These work perfectly on bare metal and virtual machines with negligible loss of performance in the case of the latter. That aside, containers are currently (inexplicably) missing other capabilities that have been assumed and idiomatic for high-performance software for decades, such as strict hardware resource control and discovery. You can sort of work around this with gross hacks but that doesn’t scale well. Basically, containers made things that were easy for decades stop working or become complicated, and these things were highly valuable for some types of software so discarding them is not an option.