A user on irc (calvin) may post here (or on this thread) later. He popped into
the channel asking about pinning a socket to a specific CPU. I pointed him at
ZMQ_AFFINITY which is available through zmq_setsockopt(). However, as he
pointed out, that only controls socket affinity with I/O threads which may
still be scheduled on any CPU.
After a little back-and-forth, here's a proposal for an addition to the C API.
void *zmq_init_with_affinity (int io_threads, char* cpu_bitmask_buffer,
size_t bitmask_len);
Such a change would allow a programmer to create a context and specify which
specific CPUs should have I/O threads pinned to them. We need to use a byte
buffer to contain the bitmask and pass a length since systems with more than 64
CPUs and/or cores are already available.
For those cases where +io_threads+ is a number larger than the number of bits
set in the bitmask, the function has three reasonable ways of treating it.
1. Round-robin assign I/O threads to the CPUs listed in the bitmask.
2. Pin the "excess" I/O threads to the last CPU listed in the bitmask.
3. Skip pinning the "excess" I/O threads to any CPU and let the scheduler float
them around as needed.
This addition would not break existing code. Furthermore, we could implement
zmq_init() internally with a call to zmq_init_with_affinity(). Passing a
zero-length buffer would skip the CPU-affinity pinning functionality (much like
option 3 above).
Feedback?
cr
_______________________________________________
zeromq-dev mailing list
[email protected]
http://lists.zeromq.org/mailman/listinfo/zeromq-dev
