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).   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  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)