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  reason).  An error value of EINVAL indicates that there had been RDMA memory
       registration already and it is therefore not safe anymore to fork.

NOTES

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

       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  directly  or  indirectly  via  a  library  such  as
       libhugetlbfs.

       Calling  ibv_fork_init()  will  reduce  performance  due to an extra system call for every
       memory registration, and the additional memory allocated to  track  memory  regions.   The
       precise performance impact depends 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>