On Fri, Aug 21, 2015 at 11:29 PM, James <wirel...@tampabay.rr.com> wrote: > Rich Freeman <rich0 <at> gentoo.org> writes: >> > for (BS) Big Science, imho. BS needs all resources solving and >> > supporting a single problem, with as low of latency as possible. > >> What kind of latency are you expecting to get with Gentoo running on >> CoreOS? A process inside a container is no different from a process >> outside a container as far as anything other than access/visibility >> goes. They're just processes as far as the kernel is concerned. >> Sure, it isn't quite booting with init=myscieneapp but it is about as >> close as you'll get to that. > > I'm not planning on running gentoo on CoreOS; so apologies if that is > confusing. I'm intending on running a stripped and optimized gentoo OS > and linux kernel as close to bare metal as I can. gcc5 is targeted at both > system, GPU and distributed resource compiling (RDMA).
Don't get me wrong - I appreciate the desire for bare-metal performance in the high-performance computing world. I've heard stories/rumors of Gentoo getting attention elsewhere in this domain, and we have a disproportionate number of physical scientists and such in the community (including probably half of the Council - we joke about it). I've even heard of Gentoo used in high-throughput trading, though a lot of that has moved on to ASICs and such and nobody talks openly about what they're doing. I was just trying to point out that containers are very different from VMs, while generally trying to solve the same sorts of problems. VMs create continuous execution overhead and are memory-expensive. Containers have zero execution overhead and are very memory-efficient. Of course, if you throw 5x as many running processes on the same PC you're still going to consume more RAM and CPU, but 5 containers running on 1 PC tend to be pretty close to the CPU+RAM requirements of linux hosts running on 5 PCs. If you're just using containers for configuration-management/etc and just run one container on a node, then you're going to be very close to the same performance you'd get running it on bare metal. >From the kernel's perspective every linux system uses containers. They just tend to use a single container. The kernel doesn't do anything differently when a process spawns in a container. When that process looks out at the world the kernel shows it everything within its namespaces. That is true whether you have one set of namespaces on the system or 50. As far as I'm aware the system calls all take just as long to run either way. Containers really are just about adding one more field to the keys in various kernel objects like processes/tasks. -- Rich
