A command-line tool to restrict a process from using particular hardware resources. It is particularly geared towards performance-sensitive multi-core experiments, in which you may want to avoid or measure the impact of CPU features like [SMT] (e.g., [Intel Hyper-Threading] or [NUMA memory]. While this is possible with existing tools like [hwloc-bind] and [numactl], it's often pretty inconvenient to get the result you want. With curb on the other hand:

console $ curb --no-smt --no-numa mycommand

You can also limit the number of cores using something like:

console $ curb --no-smt -n 3 mycommand

By default, curb picks cores, nodes, and anything else in a deterministic fashion (usually tending towards 0). If you want to pick randomly instead, use --randomize (or -r).

Passing arguments

Will run mycommand only on each physical core on a single NUMA node (the first one specifically). Note that if you want to pass additional arguments to the command under test, you can do so using --:

console $ curb --no-smt mycommand -- --no-crash --performance better

Visualizing the core allocation

To visualize what CPUs are being used using [lstopo], do:

console $ curb --no-smt --no-numa lstopo -- --pid 0

That should show all active cores in green. If you don't have a window manager running, add -v at the end and look for PUs marked with (running).

Dependencies

Curb depends on the [hwloc crate], which in turn depends on the [hwloc C library].

OS Support

Curb currently only works on cfg(unix) systems, because it sets the CPU binding [for the current process], and then calls [exec]. This should be possible to work around by instead spawning the process, getting its identifier, calling [set_cpubind_for_process], and then waiting for the process to exit. However, this has a number of downsides, like the process initially being unconstrained and having to proxy things like stdin, stdout, signals, and exit codes. Suggestions for how to support non-UNIX platforms are warmly welcome!