oracular (3) ibv_fork_init.3.gz

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>