hubbub60_pe...er_bandwidth(9)

📦 version 7.3.1, in nixpkgs unstable

✨ hubbub60_pe...er_bandwidth(9) ✨

okay so this is from the Kernel API Manual (yes, the actual kernel manual, we're fancy now 💅) and today's main character is hubbub60_perfmon_arm_measuring_out_of_order_bandwidth — bestie, the name is a whole paragraph, I know, breathe 🫶

🌸 NAME 🌸

hubbub60_perfmon_arm_measuring_out_of_order_bandwidth — literally just configures the out-of-order BW counter. that's it, that's the whole job. periodt ✨

🎀 SYNOPSIS 🎀

void hubbub60_perfmon_arm_measuring_out_of_order_bandwidth (struct hubbub *hubbub );

🦋 ARGUMENTS 🦋

  • hubbub — pointer to the hubbub hardware instance. that's your hardware bestie, hand it over and we cook 🔥

💖 DESCRIPTION 💖

So the vibe here is: we're setting up the performance monitoring counters to measure out-of-order (peak prefetch) bandwidth using hardware counters 0, 1, and 4. Three counters, three little jobs, one iconic trio 👑

  • Counter 0: the count-off counter — it counts response-valid events and gates the measurement window once it reaches its target value. lowkey the bouncer of the group, decides when the party starts 🚪
  • Counter 1: the data counter — tracks total data received during the measurement period, and generates an interrupt when measurement completes. the main character, fr fr, it's the one that actually tells you stuff 😭
  • Counter 4: the duration timer — measures elapsed time in refclk cycles. our lil stopwatch ⏱️

UTM_FILTER_SEL is set to 0 so that isolation comes from OTG-vblank gating rather than the silicon-broken HW filter. yes bestie, silicon-broken — we are not trusting that hardware filter, it's giving broken and we're moving around it 🙈

The first 200 prefetch requests are skipped (that's the ramp-up, warm-up era, we don't count those), and the subsequent 200 are the measurement window. 200 warm-up + 200 real ones. math is mathing ✨

⚠️ important caveat, do not skip: this function configures counters only. it does not turn them on. call hubbub60_perfmon_start_measuring_out_of_order_bandwidth to actually enable them. no cap, if you forget this step literally nothing happens and you'll be staring at zeros wondering why 💀

🌈 SEE ALSO 🌈

and that's the whole page, bestie 🎀 this edition came from ./drivers/gpu/drm/amd/display/... and it's dated October 2026 — mark your calendars, she's timeless 💜 slay, go measure some bandwidth 🦋

📦 where this page comes from