rdma_rw_max_send_wr(9)

📦 version 7.3.1, in nixpkgs unstable

💜 rdma_rw_max_send_wr — the vibe check on yo ur Send WR math 💜

okay so bestie, this is rdma_rw_max_send_wr(9) from the Kernel API Manual, and honestly? it's a little gift. it does one thing and it does it well: it tells you how many Send WRs you're gonna need for your RDMA read/write contexts before you even build the QP. no cap, it's the "how many snacks do I buy" of kernel RDMA. 🍓

✨ SYNOPSIS ✨

unsigned int rdma_rw_max_send_wr (struct ib_device *dev , u32 port_num ,
       unsigned int max_rdma_ctxs , u32 create_flags );

like... that's the whole signature, and yes the spacing is exactly like that, i don't make the rules 💅

🫶 ARGUMENTS 🫶

  • dev — the RDMA device. your fave. your main character. 🌈
  • port_num — the port number. which port, bestie? this one. ✨
  • max_rdma_ctxs — the number of rdma_rw_ctx structures you're working with. this is literally the number everything gets computed from, so pls count correctly 🙈
  • create_flags — QP create flags. and the important note here: pass IB_QP_CREATE_INTEGRITY_EN if data integrity will be enabled on the QP. that's a "don't forget" fr fr, because it changes the math. 🎀

🔥 DESCRIPTION 🔥

so it returns the total number of Send Queue entries needed for max_rdma_ctxs. that's the whole errand. 💖

and the result accounts for memory registration and invalidation work requests when the device requires them — like, it's not just naive multiplication, it knows your device might need extra WRs for that stuff. the way it just... handles that for you. iconic. 👑

ULPs use this to size Send Queues and Send CQs before creating a Queue Pair. so you call this first, you size your SQ and your CQ off the answer, and then you make the QP. order matters, bestie, that's the entire point. ⭐

ngl if you skip this and just vibe-guess your queue sizes, that's on you. the function is right there. 🫶

👑 SEE ALSO 👑

the whole squad, honestly. go read them, they're all friends 🦋

and that's the page, babes ✨ — brought to you by the fine folks at ./drivers/infiniband/core, dated October 2026. mwah, stan the kernel, drink water, size your queues correctly 💜🎀💅

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