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NAME

pmem2_get_flush_fn() - get a flush function

SYNOPSIS

    #include <libpmem2.h>
    typedef void (*pmem2_flush_fn)(const void *ptr, size_t size);
    struct pmem2_map;
    pmem2_flush_fn pmem2_get_flush_fn(struct pmem2_map *map);

DESCRIPTION

The pmem2_get_flush_fn() function returns a pointer to a function responsible for efficiently flushing data in the range owned by the map.

Flushing data using pmem2_flush_fn does not guarantee that the data is stored durably by the time it returns. To get this guarantee, application should either use the persist operation (see pmem2_get_persist_fn(3)) or follow pmem2_flush_fn by a drain operation (see pmem2_get_drain_fn(3)).

There are no alignment restrictions on the range described by ptr and size, but pmem2_flush_fn may expand the range as necessary to meet platform alignment requirements.

There is nothing atomic or transactional about pmem2_flush_fn. 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 pmem2_flush_fn is called to be flushed – they can be flushed at any time before pmem2_flush_fn is called.

If two (or more) mappings share the same pmem2_flush_fn and they are adjacent to each other, it is safe to call this function for a range spanning those mappings.

RETURN VALUE

The pmem2_get_flush_fn() function never returns NULL.

The pmem2_get_flush_fn() for the same map always returns the same function. This means that it’s safe to cache its return value. However, this function is very cheap (because it returns a precomputed value), so caching may not be necessary.

SEE ALSO

pmem2_get_drain_fn(3), pmem2_get_persist_fn(3), pmem2_map_new(3), libpmem2(7) and <https://pmem.io>