onload_thread_set_spin

Description

For a thread calling this function, onload_thread_set_spin() sets the per-thread spinning actions, it is not per-stack and not per-socket.

Definition

int onload_thread_set_spin(enum onload_spin_type type, unsigned spin)

Formal Parameters

type

Which operation to change the spin status of. The type must be one of the following:

enum onload_spin_type {
  ONLOAD_SPIN_ALL,        /* enable or disable all spin options */
  ONLOAD_SPIN_UDP_RECV,
  ONLOAD_SPIN_UDP_SEND,
  ONLOAD_SPIN_TCP_RECV,
  ONLOAD_SPIN_TCP_SEND,
  ONLOAD_SPIN_TCP_ACCEPT,
  ONLOAD_SPIN_PIPE_RECV,
  ONLOAD_SPIN_PIPE_SEND,
  ONLOAD_SPIN_SELECT,
  ONLOAD_SPIN_POLL,
  ONLOAD_SPIN_PKT_WAIT,
  ONLOAD_SPIN_EPOLL_WAIT,
  ONLOAD_SPIN_STACK_LOCK,
  ONLOAD_SPIN_SOCK_LOCK,
  ONLOAD_SPIN_SO_BUSY_POLL,
  ONLOAD_SPIN_TCP_CONNECT,
  ONLOAD_SPIN_MIMIC_EF_POLL, /* thread spin configuration which mimics
                              * spin settings in EF_POLL_USEC. Note
                              * that this has no effect on the
                              * usec-setting part of EF_POLL_USEC.
                              * This needs to be set separately
                              */
  ONLOAD_SPIN_MAX /* special value to mark largest valid input */
};

spin

A boolean which indicates whether the operation should spin or not.

Return Value

0 on success

-EINVAL if unsupported type is specified.

Notes

Spin time (for all threads) is set using the per-process EF_SPIN_USEC parameter.

Examples

The onload_thread_set_spin API can be used to control spinning on a per-thread or per-API basis. The existing spin-related configuration options set the default behavior for threads, and the onload_thread_set_spin API overrides the default for the thread calling this function.

Disable All Sorts of Spinning

onload_thread_set_spin(ONLOAD_SPIN_ALL, 0);

Enable All Sorts of Spinning

onload_thread_set_spin(ONLOAD_SPIN_ALL, 1);

Enable Spinning only for Certain Threads

1. Set the spin timeout by setting EF_SPIN_USEC, and disable spinning by default by setting EF_POLL_USEC=0.
2. In each thread that should spin, invoke onload_thread_set_spin().

Disable Spinning only in Certain Threads

1. Enable spinning by setting EF_POLL_USEC=<timeout>.
2. In each thread that should not spin, invoke onload_thread_set_spin().

Important: If a thread is set to NOT spin and then blocks this might invoke an interrupt for the whole stack. Interrupts occurring on moderately busy threads can cause unintended and undesirable consequences.

Enable Spinning for UDP Traffic, but not TCP Traffic

1. Set the spin timeout by setting EF_SPIN_USEC, and disable spinning by default by setting EF_POLL_USEC=0.
2. In each thread that should spin (UDP only), do:

   onload_thread_set_spin(ONLOAD_SPIN_UDP_RECV, 1)
   onload_thread_set_spin(ONLOAD_SPIN_UDP_SEND, 1)

Enable Spinning for TCP Traffic, but not UDP Traffic

1. Set the spin timeout by setting EF_SPIN_USEC, and disable spinning by default by setting EF_POLL_USEC=0.
2. In each thread that should spin (TCP only), do:

   onload_thread_set_spin(ONLOAD_SPIN_TCP_RECV, 1)
   onload_thread_set_spin(ONLOAD_SPIN_TCP_SEND, 1)
   onload_thread_set_spin(ONLOAD_SPIN_TCP_ACCEPT, 1)

Spinning and Sockets

When a thread calls onload_thread_set_spin() it sets the spinning actions applied when the thread accesses any socket - irrespective of whether the socket is created by this thread.

If a socket is created by thread-A and is accessed by thread-B, calling onload_thread_set_spin(ONLOAD_SPIN_ALL, 1) only from thread-B will enable spinning for thread-B, but not for thread-A. In the same scenario, if onload_thread_set_spin(ONLOAD_SPIN_ALL, 1) is called only from thread-A, then spinning is enabled only for thread-A, but not for thread-B.

The onload_thread_set_spin() function sets the per-thread spinning action.