NAME

       ibv_fork_init - initialize libibverbs to support fork()

SYNOPSIS

              #include <infiniband/verbs.h>

              int ibv_fork_init(void);

DESCRIPTION

       ibv_fork_init()  initializes  libibverbs’s  data structures to handle fork() function calls correctly and
       avoid data corruption, whether fork() is called explicitly or implicitly (such as in system()).

       It is not necessary to use this function if all parent process threads are always blocked until all child
       processes end or change address spaces via an exec() operation.

RETURN VALUE

       ibv_fork_init() returns 0 on success, or the value of errno on failure (which indicates the failure  rea‐
       son).

NOTES

       ibv_fork_init()  works on Linux kernels supporting the MADV_DONTFORK flag for madvise() (2.6.17 and high‐
       er).

       Setting the environment variable  RDMAV_FORK_SAFE  or  IBV_FORK_SAFE  has  the  same  effect  as  calling
       ibv_fork_init().

       Setting the environment variable RDMAV_HUGEPAGES_SAFE tells the library to check the underlying page size
       used by the kernel for memory regions.  This is required if an application uses huge pages either direct‐
       ly or indirectly via a library such as libhugetlbfs.

       Calling  ibv_fork_init()  will  reduce performance due to an extra system call for every memory registra‐
       tion, and the additional memory allocated to track memory regions.  The precise  performance  impact  de‐
       pends on the workload and usually will not be significant.

       Setting RDMAV_HUGEPAGES_SAFE adds further overhead to all memory registrations.

SEE ALSO

       exec(3), fork(2), ibv_get_device_list(3), system(3), wait(2)

AUTHOR

       Dotan Barak <dotanba@gmail.com>

libibverbs                                         2006-10-31                                   IBV_FORK_INIT(3)