xs_tcp_write_space(9)

📦 version 7.3.1, in nixpkgs unstable

🌸 xs_tcp_write_space(9) — like, the socket write-space callback 🌸

okay bestie, welcome to the xs_tcp_write_space(9) page, live from the Kernel API Manual 💖 this one is short and sweet but she is important, so let's get into it.

✨ NAME ✨

xs_tcp_write_space — the callback that gets invoked when socket buffer space becomes available 🎀

🦋 SYNOPSIS 🦋

void xs_tcp_write_space (struct sock *sk );

that's it. that's the whole signature. no cap. 💅

🌸 ARGUMENTS 🌸

  • sk — the socket whose state has changed, bestie. that's the one we're talking about 🫶

💜 DESCRIPTION 💜

So here's the vibe: this gets called when more output buffer space is available for this socket ✨ that's the whole trigger, no secret lore.

But here's the part everyone always asks about — we do not just immediately wake up our writers the second there's a crumb of space. nope! we try not to wake our writers until they can make "significant" progress 👑

why? because otherwise we'll waste resources thrashing kernel_sendmsg with a bunch of small requests 😭 like, imagine waking someone up for one single grape. embarrassing. so we wait until there's actually enough room for the writers to do something real. main character energy only. 🔥

fr fr, the whole point of not waking writers early is so we're not out here burning resources on tiny sends. respect the buffer. 🌈

👑 SEE ALSO 👑

Kernel file ./net/sunrpc/xprtsock.c plus literally all of these:

okay that's the page!! go read the rest of the xprtsock girlies when you're done, they all live together 💅

this came from ./net/sunrpc, dated October 2026 — mwah, sending you off with a kiss 🫶✨🎀

📦 where this page comes from