NAME

       pmemobj_memcpy_persist(), pmemobj_memset_persist(), pmemobj_persist(), pmemobj_flush(), pmemobj_drain() -
       low-level memory manipulation functions

SYNOPSIS

              #include <libpmemobj.h>

              void *pmemobj_memcpy_persist(PMEMobjpool *pop, void *dest,
                  const void *src, size_t len);
              void *pmemobj_memset_persist(PMEMobjpool *pop, void *dest,
                  int c, size_t len);
              void pmemobj_persist(PMEMobjpool *pop, const void *addr,
                  size_t len);
              void pmemobj_flush(PMEMobjpool *pop, const void *addr,
                  size_t len);
              void pmemobj_drain(PMEMobjpool *pop);

DESCRIPTION

       The  libpmemobj-specific low-level memory manipulation functions described here leverage the knowledge of
       the additional configuration options available for libpmemobj(7) pools, such as replication.   They  also
       take  advantage  of the type of storage behind the pool and use appropriate flush/drain functions.  It is
       advised to use these functions in conjunction with libpmemobj(7) objects rather than using low-level mem‐
       ory manipulation functions from libpmem.

       The pmemobj_memcpy_persist() and pmemobj_memset_persist() functions provide the same  memory  copying  as
       their  namesakes memcpy(3), and memset(3), and ensure that the result has been flushed to persistence be‐
       fore returning.

       pmemobj_persist() forces any changes in the range [addr, addr+len) to be  stored  durably  in  persistent
       memory.   Internally  this  may call either pmem_msync(3) or pmem_persist(3).  There are no alignment re‐
       strictions on the range described by addr and len, but pmemobj_persist() may expand the range  as  neces‐
       sary to meet platform alignment requirements.

              WARNING:  Like  msync(2), there is nothing atomic or transactional about this call.  Any unwritten
              stores in the given range will be written, but some stores may have already been written by virtue
              of normal cache eviction/replacement policies.  Correctly written code must not depend  on  stores
              waiting until pmemobj_persist() is called to become persistent - they can become persistent at any
              time before pmemobj_persist() is called.

       The pmemobj_flush() and pmemobj_drain() functions provide partial versions of the pmemobj_persist() func‐
       tion  described  above.  These functions allow advanced programs to create their own variations of pmemo‐
       bj_persist().  For example, a program that needs to flush several discontiguous ranges  can  call  pmemo‐
       bj_flush()  for  each  range and then follow up by calling pmemobj_drain() once.  For more information on
       partial flushing operations, see pmem_flush(3).

RETURN VALUE

       The pmemobj_memcpy_persist() and pmemobj_memset_persist() functions return the same values as their name‐
       sakes memcpy(3), and memset(3).

       pmemobj_persist(), pmemobj_flush() and pmemobj_drain() return no value.

EXAMPLES

       The following code is functionally equivalent to pmemobj_memcpy_persist():

              void *
              pmemobj_memcpy_persist(PMEMobjpool *pop, void *dest,
                  const void *src, size_t len)
              {
                  void *retval = memcpy(dest, src, len);

                  pmemobj_persist(pop, dest, len);

                  return retval;
              }

       pmemobj_persist() can be thought of as this:

              void
              pmemobj_persist(PMEMobjpool *pop, const void *addr, size_t len)
              {
                  /* flush the processor caches */
                  pmemobj_flush(pop, addr, len);

                  /* wait for any pmem stores to drain from HW buffers */
                  pmemobj_drain(pop);
              }

SEE ALSO

       memcpy(3), memset(3), pmem_msync(3), pmem_persist(3), libpmem(7) libpmemobj(7) and <http://pmem.io>

PMDK - pmemobj API version 2.3                     2018-05-21                          PMEMOBJ_MEMCPY_PERSIST(3)