rpc_update_rtt(9)

💅 rpc_update_rtt(9) — the Kernel API Manual, bestie edition 🎀

okay so real talk: this is a page from the Kernel API Manual, section 9, and the star of the show is rpc_update_rtt(9). yes it's a mouthful, no you don't have to say it out loud. let's get into it ✨

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🌸 NAME 🌸

rpc_update_rtt — update an RPC RTT estimator context, periodt 💖

✨ SYNOPSIS ✨

void rpc_update_rtt (struct rpc_rtt *rt , unsigned int timer , long m );

that's the whole vibe. no return value, it just does the thing 🫶

🦋 ARGUMENTS 🦋

• rt — the context you're updating. like, the little state blob that's about to get a glow-up 💅
• timer — the index into the timer array, aka which request type we're talking about 🔥
• m — the recent actual RTT, measured in jiffies, no cap ⏱️

👑 DESCRIPTION 👑

okay so here's the one thing you cannot skip, bestie — read it twice:

NB: when you're computing the smoothed RTT and the standard deviation, be careful not to produce negative intermediate results. 🚨

like, the math is giving "trust me bro" energy and if you let it go negative mid-computation you're gonna have a bad time 😭 so watch those intermediate values, fr fr.

🌈 SEE ALSO 🌈

• kernel file ./net/sunrpc/timer.c
• rpc_init_rtt(9) — the setup girly 🧚
• rpc_calc_rto(9) — the one that does the timeout math 💜

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and that's the whole page, you ate that 💅✨

cute little sign-off for the credits: this one lives under ./net/sunrpc and it's stamped October 2026 🍓 see you in the group chat 🫶