PMEM2_GET_DRAIN_FN(3)

✨ pmem2_get_drain_fn() — get a drain function ✨

okay bestie, welcome to the PMDK Programmer's Manual 💖 this one's a lil baby page but it's IMPORTANT, so grab your iced coffee and let's go 🧚

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🌸 NAME 🌸

pmem2_get_drain_fn() — get a drain function

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🎀 SYNOPSIS 🎀

#include <libpmem2.h>

typedef void (*pmem2_drain_fn)(void);

struct pmem2_map;

pmem2_drain_fn pmem2_get_drain_fn(struct pmem2_map *map);

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💅 DESCRIPTION 💅

so. pmem2_get_drain_fn() hands you back a pointer to a function — and that function's whole job is to drain flushes efficiently (the flushes from pmem2_get_flush_fn(3), iykyk) in the range that map owns. 👑

and what does "draining" even mean here, bestie? it means making sure the flushes that happened before this operation don't get reordered to after it. periodt. 🔥

ngl it's not strictly true, but you can lowkey think of draining as just waiting for the previous flushes to finish. that's the vibe. ✨

also — and this is the good part — 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. no cap. 🫶

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🌈 RETURN VALUE 🌈

pmem2_get_drain_fn() never returns NULL. not ever. 💀🙈

and for the same map, it always returns the same function. which means it's totally safe to cache its return value, bestie — go off. 💅

that said… this function is very cheap (it just returns a precomputed value, main character behavior honestly), so caching might not even be necessary. your call. 🦋

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⭐ SEE ALSO ⭐

• pmem2_get_flush_fn(3)
• pmem2_get_persist_fn(3)
• pmem2_map_new(3)
• libpmem2(7)
• https://pmem.io

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💌 and that's the whole page, bestie — go drain those flushes and slay 💖

this icon was brought to you by PMDK, dated 2025-07-24 — mwah, catch you in the next manpage 🎀🌸✨