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Env

Concept​

Photon Env consists of different kinds of engines and a simulated coroutine stack in userspace.

Namespace​

photon::

Headers​

<photon/photon.h>

API​

init​

int photon::init(uint64_t event_engine = INIT_EVENT_DEFAULT, uint64_t io_engine = INIT_IO_DEFAULT);

Description​

Initialize the coroutine stack on current vCPU. Next, you can create multiple Photon threads via thread_create, and migrate them to other vCPUs. You should NOT invoke blocking function calls from now on.

The event_engine is platform independent. It cooperates with the scheduler and decides the way it polls fd and processes events. Usually we would do a non-blocking wait for events on a thread, making the caller thread fall to SLEEPING. After the events being processed, it's the engine's responsibility to interrupt the caller thread and make it READY.

The io_engine will setup ancillary threads running in the background, if necessary.

Parameters​

  • event_engine Supported types are:

    • INIT_EVENT_NONE None, only used in test.
    • INIT_EVENT_DEFAULT It will first try io_uring, then choose epoll if io_uring failed.
    • INIT_EVENT_EPOLL
    • INIT_EVENT_IOURING
    • INIT_EVENT_KQUEUE Only avalaible on macOS or FreeBSD.

  • io_engine Supported types are:

    • INIT_IO_NONE Don't need any additional IO engines. Just use libc's read/write, or io_uring's async IO if its event_engine is set.
    • INIT_IO_LIBAIO
    • INIT_IO_LIBCURL
    • INIT_IO_SOCKET_EDGE_TRIGGER
    • INIT_IO_EXPORTFS
    • INIT_IO_FSTACK_DPDK
info

Running an IOURING event engine would need the kernel version to be greater than 5.8. We encourage you to upgrade to the latest kernel so that you could enjoy the extraordinary performance.

Return​

Returns 0 on success, returns -1 on error.

fini​

int photon::fini();

Description​

Destroy and join the ancillary threads of the io engine. Stop the event engine. Deallocate the coroutine stack.

Parameters​

None

Return​

Returns 0 on success, returns -1 on error.