LIBPFM(3)

✨ LIBPFM(3) — the snbep_unc_unc_pcu glow-up ✨

okay bestie, this is the libpfm page for libpfm_intel_snbep_unc_pcu — aka the Intel Sandy Bridge-EP Power Controller Unit (PCU) uncore PMU support. yes the name is a mouthful. no we're not renaming it. 💅

🎀 NAME 🎀

libpfm_intel_snbep_unc_pcu — support for Intel Sandy Bridge-EP Power Controller Unit (PCU) uncore PMU

🦋 SYNOPSIS 🦋

#include <perfmon/pfmlib.h>

PMU name: snbep_unc_pcu
PMU desc: Intel Sandy Bridge-EP PCU uncore PMU

💖 DESCRIPTION 💖

So like, this library ships support for the Intel Sandy Bridge Power Controller Unit uncore PMU. iconic behavior tbh.

ngl there's a catch though: this PMU model only exists on Sandy Bridge model 45. and there's literally only one PCU PMU per processor socket. one. singular. main character energy, no understudies. 👑

🌸 MODIFIERS 🌸

The following modifiers are supported on Intel Sandy Bridge C-Box uncore PMU:

• i — Invert the meaning of the event. The counter will now count HA cycles in which the event is not occurring. This is a boolean modifier. not me flipping the whole vibe of your counter 🙈
• e — Enable edge detection, i.e., count only when there is a state transition from no occurrence of the event to at least one occurrence. This modifier must be combined with a threshold modifier (t) with a value greater or equal to one. This is a boolean modifier. fr fr, don't run e solo, it needs its buddy.
• t — Set the threshold value. When set to a non-zero value, the counter counts the number of HA cycles in which the number of occurrences of the event is greater or equal to the threshold. This is an integer modifier with values in the range [0:15]. that's it, that's the whole range, bestie.
• ff — Enable frequency band filtering. This modifier applies only to the UNC_P_FREQ_BANDx_CYCLES events, where x is [0-3]. The modifiers expects an integer in the range [0-255]. The value is interpreted as a frequency value to be multiplied by 100Mhz. Thus if the value is 32, then all cycles where the processor is running at 3.2GHz and more are counted. 3.2GHz and up?? highkey slay ⚡

🌈 Frequency band filtering 🌈

There are 3 events which support frequency band filtering, namely, UNC_P_FREQ_BAND0_CYCLES, UNC_P_FREQ_BAND1_CYCLES, UNC_P_FREQ_BAND2_CYCLES, UNC_P_FREQ_BAND3_CYCLES. (yes bestie, "3 events" then four names. we don't make the rules, we just pass them along verbatim 💀)

The frequency filter (available via the ff modifier) is stored into a PMU shared register which hold all 4 possible frequency bands, one per event. However, the library generate the encoding for each event individually because it processes events one at a time. The caller or the underlying kernel interface may have to merge the band filter settings to program the filter register properly.

⚠️ heads up: that shared register means you (or the kernel interface underneath you) might have to do the merging yourself. the library is doing one event at a time and it's not gonna do that part for you. plan accordingly 🫶

💜 AUTHORS 💜

Stephane Eranian <eranian@gmail.com>

and that's the whole page, periodt ✨ this was Linux Programmer's Manual, LIBPFM(3), dated August, 2012 — ty for coming to my ted talk, ily, go count some uncore events 🎀🦋💖