libibverbs | allows programs to use RDMA

When running applications that use libibverbs under the Valgrind memory-checking debugger, Valgrind will falsely report "read from uninitialized" for memory that was initialized by the kernel drivers. Specifically, Valgrind cannot see when kernel drivers write to userspace memory, so when the process reads from that memory, Valgrind incorrectly assumes that the memory contents are uninitialized, and therefore raises a warning. libibverbs can be built with specific support for the Valgrind memory-checking debugger by specifying the --with-valgrind command line argument to configure. This flag enables code in libibverbs to tell Valgrind "this memory may look uninitialized, but it’s really OK," which therefore suppresses the incorrect "read from uninitialized" warnings. This code adds trivial overhead to the critical performance path, so it is disabled by default. The intent is that production users can use a "normal" build of libibverbs and developers can use the "valgrind debug" build by simply switching their LD_LIBRARY_PATH environment variables. Libibverbs needs some header files from Valgrind in order to compile this support; it is important to use the header files from the same version of Valgrind that will be used at run time. You may need to specify the directory where Valgrind’s header files are installed as an argument to --with-valgrind. For example. will make the libibverbs build look for valgrind headers in /opt/valgrind/include.