Delivering timer "interrupts" to userspace in the least hygienic way.
This project is comprised of two parts: a kernel module to allow low latency heartbeats to be delivered to the userspace, and a userspace library designed to interface with the kernel module. There are also a set of example programs that use the library.
To compile the library:
$ make
To compile the kernel module:
$ make kmod
You can also insert the kernel module using make ins and make rm to remove it.
Once you have it built, the entire API is located in include/heartbeat.h. On each thread that
wants to receive heartbeat interrupts, you must call hb_init(core), which locks the thread
to a certain core. We lock the thread to a core to avoid the overhead of an IPI or signalling.
Once initialized, a heartbeat can be scheduled using hb_oneshot(us, cb), where after us
microseconds (±~1us), the function cb will be called. You must schedule another heartbeat
afterwards when using this interface.
hb_repeat(us, cb) works in a similar way, but you do not need to call hb_oneshot after
cb is called, resulting in almost no overhead. Note, however, that extremely low intervals
using repeat results in missed interrupts, as a heartbeat may occur during your callback,
and reentrancy is not supported.
Before exiting the thread using heartbeats, be sure to call hb_exit()