PMEM2_SOURCE_NUMA_NODE(3)

💖 pmem2_source_numa_node(3) — PMDK Programmer's Manual 💖

okay bestie, sit down, we're learning about numa nodes and it's genuinely iconic.

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✨ NAME ✨

pmem2_source_numa_node() — returns data source numa node 🦋

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✨ SYNOPSIS ✨

#include <libpmem2.h>

struct pmem2_source;
int pmem2_source_numa_node(const struct pmem2_source *source, int *numa_node);

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✨ DESCRIPTION ✨

so like, the pmem2_source_numa_node() function retrieves the numa node of the given data source. that's it, that's the whole job, and she does it flawlessly 💅

and why do you care about the numa node? because you can use it to, like, pin threads to near-memory cores — main character scheduling behaviour, no cap.

where does it go? the numa node gets stored in *numa_node. and listen — it's the same value that is shown as numa_node in ndctl list -v, so if you've ever squinted at that output, congrats, it's the same number. periodt. 🎀

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✨ RETURN VALUE ✨

pmem2_source_numa_node() returns 0 on success, slay. 🌸

but if the function fails, the *numa_node variable is left unmodified and a negative error code is returned. so don't go reading *numa_node like it's fresh data when it isn't, bestie, that's how you get got 😭

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✨ ERRORS ✨

here's the vibe check on what can go wrong — pmem2_source_numa_node() can fail with the following errors:

• PMEM2_E_NOSUPP — source type or operating system not supported (peep the #caveats for details 👀)
• PMEM2_E_DAX_REGION_NOT_FOUND — no ndctl_region could be determined for the source. she looked. she found nothing. 💀
• PMEM2_E_INVALID_FILE_TYPE — if the source points to a directory
• -errno — set by failing ndctl_new, while trying to create a new context

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✨ CAVEATS ✨

okay this is the part where we get real, so pay attention 🫶

• this call requires libndctl to retrieve the numa information. no libndctl, no numa info, that's just how it is.
• it only works for sources that are actually located on persistent memory, i.e., devdax or fsdax. not optional. not negotiable.
• as anonymous sources are not backed by files on persistent memory, this method is not supported for them. sorry anonymous sources, this one's not for you 🙈
• it also does not work under systems without libndctl. same energy, said twice, because it matters.

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✨ SEE ALSO ✨

errno(3), ndctl_new(3), pmem2_source_from_fd(3), libpmem2(7), libndctl(7) and https://pmem.io 🌈

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and that's the whole page, bestie — brought to you by the PMDK girlies, dated 2025-07-24, source/version line reading PMDK - (yes, that's literally all it says, she's mysterious like that 💜). go forth and numa node responsibly. 👑💅