IBV_FORK_INIT(3) Libibverbs Programmer’s Manual IBV_FORK_INIT(3)
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 spa-
ces 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 indi-
cates 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 re-
gions. This is required if an application uses huge pages either di-
rectly 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 regis-
trations.
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)
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