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NAME

pmem2_get_drain_fn() - get a drain function

SYNOPSIS

    #include <libpmem2.h>
    typedef void (*pmem2_drain_fn)(void);
    struct pmem2_map;
    pmem2_drain_fn pmem2_get_drain_fn(struct pmem2_map *map);

DESCRIPTION

The pmem2_get_drain_fn() function returns a pointer to a function responsible for efficiently draining flushes (see pmem2_get_flush_fn(3)) in the range owned by map. Draining, in this context, means making sure that the flushes before this operation won’t be reordered after it. While it is not strictly true, draining can be thought of as waiting for previous flushes to complete.

If two (or more) mappings share the same drain function, it is safe to call this function once for all flushes belonging to those mappings.

RETURN VALUE

The pmem2_get_drain_fn() function never returns NULL.

The pmem2_get_drain_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_flush_fn(3), pmem2_get_persist_fn(3), pmem2_map_new(3), libpmem2(7) and <https://pmem.io>