ib_alloc_mr(9)

💅 ib_alloc_mr(9) — the kernel API manual, bestie edition 🎀

okay so real talk: this is a page from the Kernel API Manual, and the star of the show is ib_alloc_mr(9) — literally the function that hands you a memory region. let's get into it ✨

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🌸 NAME 🌸

ib_alloc_mr — allocates a memory region. that's it, that's the whole vibe. one job, does it well 👑

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⭐ SYNOPSIS ⭐

struct ib_mr * ib_alloc_mr (struct ib_pd *pd , enum ib_mr_type mr_type ,
u32 max_num_sg );

look at that signature. gorgeous. returns a struct ib_mr * and takes three args, we love a clean three-arg moment 🫶

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🦋 ARGUMENTS 🦋

• pd — the protection domain that's associated with the region. like, which PD is this MR even living in? that one 💖
• mr_type — the type of the memory region. it's an enum ib_mr_type, so pick your flavor ✨
• max_num_sg — the maximum number of sg entries available for registration. the ceiling. the limit. the "no more than this, babes" 🚧

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💀 NOTES 💀

okay important, listen up 🙈

• Memory registration page/sg lists must not exceed max_num_sg. that's a hard no-cap limit, fr fr.
• For mr_type IB_MR_TYPE_MEM_REG, the total length cannot exceed max_num_sg * used_page_size. do the math before you vibe check your buffers, i'm begging 😭

ngl, these are the kind of notes you skim and then regret skimming. please read them. 💅

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🌈 SEE ALSO 🌈

kernel file ./drivers/infiniband/core/verbs.c (__ib_alloc_pd(9)), plus the whole friend group:

• ib_dealloc_pd_user(9)
• rdma_copy_ah_attr(9)
• rdma_replace_ah_attr(9)
• rdma_move_ah_attr(9)
• rdma_create_ah(9)
• rdma_create_user_ah(9)
• rdma_move_grh_sgid_attr(9)
• rdma_destroy_ah_attr(9)
• ib_create_srq_user(9)
• ib_create_qp_user(9)
• ib_resolve_eth_dmac(9)
• ib_modify_qp_with_udata(9)
• ib_alloc_mr_integrity(9)
• ib_alloc_xrcd_user(9)
• ib_dealloc_xrcd_user(9)
• ib_create_wq(9)
• ib_destroy_wq_user(9)
• ib_map_mr_sg_pi(9)
• ib_map_mr_sg(9)
• ib_sg_to_pages(9)
• ib_drain_sq(9)
• ib_drain_rq(9)
• ib_drain_qp(9)
• rdma_alloc_hw_stats_struct(9)
• rdma_free_hw_stats_struct(9)

like, the entire roster. main character energy from every single one of them 👑

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and that's a wrap, bestie 🎀 this little guy lives over in ./drivers/infiniband/core and this edition is dated October 2026 — see you in the next kernel cycle, mwah 💜🧚