Update content for md

8 files changed, 461 insertions, 171 deletions

diff --git a/gemfeed/DRAFT-unveiling-ior-ng.md b/gemfeed/DRAFT-unveiling-ior-ng-part-1.md
index 304d92aa..21b9f7eb 100644
--- a/gemfeed/DRAFT-unveiling-ior-ng.md
+++ b/gemfeed/DRAFT-unveiling-ior-ng-part-1.md
@@ -1,22 +1,21 @@
-# Unveiling I/O Riot NG
+# Unveiling I/O Riot NG — Part 1: a guided tour
 
 > Draft — not in the gemfeed yet. Promote with the usual rename + index dance.
 
-I rewrote I/O Riot. The old one was C + Systemtap and dates from 2017. The new one — call it ior — is Go + C + BPF via libbpfgo, runs on Linux, and is mostly a TUI dashboard rather than a record/replay box. Since pictures are worth more than yet another README table of key bindings, I built a demo.
+I rewrote I/O Riot. The old one was C + Systemtap and dates from 2017. The new one — call it ior — is Go + C + BPF via libbpfgo, runs on Linux, and is mostly a TUI dashboard rather than a record/replay box. Since pictures are worth more than yet another README table of key bindings, I am presenting some examples in this post.
+
+This is the first of three posts. Part 1 is the demo-driven tour: what ior looks like, how the dashboard tabs work, how the live flamegraph reads, how filtering and recording work. Part 2 covers installing it on a fresh Rocky Linux 9 box and the "compile once, run everywhere" story underneath that — eBPF, CO-RE, libbpfgo, static linking, and why a 23 MB binary you build on one machine just runs on every other Linux host you scp it to. Part 3 is the under-the-hood companion — the per-event schema, the syscall-coverage probe generator, async-syscall caveats, and post-mortem SQL on the parquet output. The three are independent; read them in any order.
 
 [![ior's live flamegraph: every running process, by file path, by syscall — width = event volume](./unveiling-ior-ng/00-hero-flamegraph.png "ior's live flamegraph: every running process, by file path, by syscall — width = event volume")](./unveiling-ior-ng/00-hero-flamegraph.png)  
 
+
 [I/O Riot NG on Codeberg](https://codeberg.org/snonux/ior)  
 [the original I/O Riot post (2018)](./2018-06-01-realistic-load-testing-with-ioriot-for-linux.md)  
 
 ## Table of Contents
 
-* [⇢ Unveiling I/O Riot NG](#unveiling-io-riot-ng)
+* [⇢ Unveiling I/O Riot NG — Part 1: a guided tour](#unveiling-io-riot-ng--part-1-a-guided-tour)
 * [⇢ ⇢ What it does](#what-it-does)
-* [⇢ ⇢ A short detour: eBPF and libbpfgo](#a-short-detour-ebpf-and-libbpfgo)
-* [⇢ ⇢ ⇢ CO-RE — the part that makes ior actually portable](#co-re--the-part-that-makes-ior-actually-portable)
-* [⇢ ⇢ ⇢ If you want to go deeper](#if-you-want-to-go-deeper)
-* [⇢ ⇢ The whole thing as a tape pipeline](#the-whole-thing-as-a-tape-pipeline)
 * [⇢ ⇢ First launch](#first-launch)
 * [⇢ ⇢ The seven tabs, in 30 seconds each](#the-seven-tabs-in-30-seconds-each)
 * [⇢ ⇢ ⇢ `2` Overview](#2-overview)
@@ -28,100 +27,17 @@ I rewrote I/O Riot. The old one was C + Systemtap and dates from 2017. The new o
 * [⇢ ⇢ The Stream tab is the good one](#the-stream-tab-is-the-good-one)
 * [⇢ ⇢ Filtering, more thoroughly](#filtering-more-thoroughly)
 * [⇢ ⇢ Recording](#recording)
-* [⇢ ⇢ Querying a parquet trace with ClickHouse](#querying-a-parquet-trace-with-clickhouse)
-* [⇢ ⇢ Reproducing the whole demo](#reproducing-the-whole-demo)
+* [⇢ ⇢ Installing it](#installing-it)
 * [⇢ ⇢ What's still missing](#what-s-still-missing)
 
 ## What it does
 
-ior attaches BPF tracepoints to a chunk of the synchronous-I/O syscall surface — open, read, write, stat, mmap, sync, link, fcntl, dup, the obvious ones. Each enter/exit pair becomes an event with a duration plus an inter-syscall gap, and the events feed a Bubble Tea dashboard with seven tabs: a live flamegraph, an overview, sortable per-syscall / per-file / per-process tables, latency histograms, and a live event stream with a stackable filter UI on top.
+ior attaches BPF tracepoints to a chunk of the synchronous-I/O syscall surface — open, read, write, stat, mmap, sync, link, fcntl, dup, the obvious ones — plus the async ones (`io_uring_*`, `aio_*`). Each enter/exit pair becomes an event with a duration plus an inter-syscall gap, and the events feed a Go Bubble Tea dashboard with seven tabs: a live flamegraph, an overview, sortable per-syscall / per-file / per-process tables, latency histograms, and a live event stream with a stackable filter UI on top.
 
 Same shape as the old I/O Riot in spirit: capture what the system is actually doing, not synthetic load. Different shape in execution: no replay engine, no separate record file unless you ask for one, no kernel-debug-info dance.
 
 [![I/O Riot NG logo](./unveiling-ior-ng/00-logo.png "I/O Riot NG logo")](./unveiling-ior-ng/00-logo.png)  
 
-## A short detour: eBPF and libbpfgo
-
-If you haven't touched eBPF before: it's a small in-kernel bytecode VM. You compile a tiny C program, the kernel verifies it can't crash or loop forever, and then it runs every time some hook fires — a syscall enter/exit, a kprobe, a tracepoint, a network packet. The program writes events into a ring buffer that userspace mmaps and drains. No kernel module, no patched kernel, no debug symbols required.
-
-ior plugs into the syscall tracepoints — `sys_enter_openat`, `sys_exit_read`, etc. — and the BPF side does the bare minimum: timestamp the event, copy a few fields, push to a perf ring buffer. All the heavy lifting (string interning, latency math, aggregation, the dashboard) is in Go on the userspace side.
-
-The kernel ships a C library called libbpf that handles loading the program, attaching it to hooks, managing maps, and reading the ring buffer. There are two well-known ways to drive that from Go:
-
-* libbpfgo (Aqua Security): a thin cgo wrapper around libbpf. You ship libbpf along with your binary and call into the same C API that `bpftool` and `perf` use.
-* cilium/ebpf: a from-scratch pure-Go reimplementation of everything libbpf does — ELF parser, BTF resolver, syscall layer, the lot.
-
-I went with libbpfgo specifically because it's a wrapper, not a reimplementation. Whatever lands in libbpf upstream — new map types, new attach kinds, CO-RE fixes — I get for free the next kernel cycle. The pure-Go variant has to chase libbpf's feature set in parallel, and any divergence is on me to debug. For a tracer that's mostly value-add on the userspace side, "be a thin client of the kernel's own library" wins.
-
-### CO-RE — the part that makes ior actually portable
-
-The old I/O Riot was Systemtap. Systemtap programs are translated into a kernel module against the running kernel's exact headers, and that module then has to be loaded with `insmod`. That meant: the user has to install a kernel-debuginfo package matching their running kernel, and a fresh build per host (or per kernel update). On the BSD-style "you only run what you compiled here" laptop crowd that was tolerable; on a fleet of distros + kernel versions it was a recurring tax. Half of the original I/O Riot's README was about kernel-debuginfo dance steps.
-
-CO-RE — Compile Once, Run Everywhere — is the eBPF feature that throws all of that out. The idea, in one paragraph: when you write a BPF program that reads `task->mm->start_stack`, you don't bake the offsets of those fields into the compiled program. Instead, the compiler emits relocation records ("at this instruction, fetch the offset of `mm` inside `task_struct`"). At load time, libbpf looks up the actual offsets in the target kernel's BTF (BPF Type Format — a description of every kernel struct, embedded in `/sys/kernel/btf/vmlinux` on any modern kernel) and patches the program in place. The same `.bpf.o` that ran on a 5.10 Debian kernel runs on a 6.8 Fedora kernel without recompilation.
-
-Pictorially, the contrast looks like this:
-
-```
-Old I/O Riot (Systemtap)                 New ior (libbpf + CO-RE)
-─────────────────────────                ────────────────────────────
-  .stp source                              .bpf.c source
-       │                                        │
-       │ needs THIS kernel's headers            │ build ONCE against vmlinux.h
-       │ + debuginfo package installed          │ (generated from any kernel BTF)
-       ▼                                        ▼
-  per-host translate + compile              one portable .bpf.o
-       │                                        │
-       ▼                                        ▼
-  per-host kernel module                    same binary on every host
-       │                                        │
-  insmod / modprobe                         libbpf loader:
-       │                                        │  • read /sys/kernel/btf/vmlinux
-       ▼                                        │  • patch field offsets
-  attached, this kernel only                 │  • verify + load
-                                              ▼
-                                          attached, runs anywhere
-```
-
-What that buys ior in practice: I ship a single `ior` binary. On any Linux ≥4.18-ish with BTF available (which is almost all of them now — Debian, Ubuntu, Fedora, Arch, RHEL all ship `CONFIG_DEBUG_INFO_BTF=y` by default), it just works. No kernel-debuginfo dependency, no per-kernel build matrix, no DKMS hooks. The first time I tried `scp ior fedora-box:` and it ran without complaint after a 6-month gap I had to double-check it wasn't silently doing nothing.
-
-The runtime shape of a trace pipeline lines up with that:
-
-```
- kernel side                                userspace (this binary)
- ───────────                                ───────────────────────
-                                            ┌──────────────────────┐
-   tracepoint:                              │  Go process          │
-   sys_enter_openat                         │  ┌────────────────┐  │
-        │                                   │  │  aggregator    │  │
-        ▼                                   │  │  (latency,     │  │
-   ┌─────────┐                              │  │   stacks,      │  │
-   │ BPF prog│ ─── perf ring buf ──────────>│──│   filters)     │  │
-   │ (verified                              │  └─────┬──────────┘  │
-   │  bytecode)                             │        │             │
-   └─────────┘                              │        ▼             │
-                                            │  Bubble Tea TUI /    │
-                                            │  parquet writer /    │
-                                            │  CSV stdout          │
-                                            └──────────────────────┘
-```
-
-The cost is cgo. Every call from Go into libbpf crosses the cgo boundary, which historically meant tens to ~hundred-ish nanoseconds of overhead per call — register save/restore, a stack switch onto g0, goroutine state bookkeeping. Cheap in absolute terms, but it adds up if you call into C inside a tight loop. ior keeps the actual hot path on the kernel side and only crosses into Go once per drained batch of events from the ring buffer, so the per-call cost is amortized over thousands of events. In practice it doesn't show up in profiles.
-
-Go 1.26, the current release at the time of writing (late April 2026), is the one that finally took a serious bite out of cgo's per-call cost — the runtime can elide a chunk of the bookkeeping for calls that don't need it. Real-world wins depend heavily on the workload, but the rough direction is that cgo now feels closer to "an unusually expensive function call" than to "a context switch", which is the right mental model for almost everyone touching a C library from Go. The shorter version: cgo overhead used to be a real footgun for ports that called into C in the inner loop. With Go 1.26 it's a footnote unless you're doing many millions of small calls per second, in which case batching across the boundary still fixes it.
-
-### If you want to go deeper
-
-If any of this sounds interesting and you want to learn how to write your own BPF programs, two books are the standard recommendations and both well worth the time:
-
-* "Learning eBPF" by Liz Rice (O'Reilly, 2023) is the friendlier on-ramp. It walks through writing your first programs end-to-end, covers CO-RE and BTF in plain English, and is the book I'd hand to someone who has never touched the kernel side before. Liz also gave the canonical "what is eBPF" conference talk floating around YouTube, which makes a good 40-minute companion.
-* "BPF Performance Tools: Linux System and Application Observability" by Brendan Gregg (Addison-Wesley, 2019) is the encyclopedia. It's where you go after you've understood the basics and now want a complete reference for tracing every subsystem in the kernel — file systems, networking, scheduler, languages, applications — with worked tools for each. The flame-graph-driven analysis style throughout is also exactly how ior's own flamegraph tab thinks about a workload.
-
-Between the two, Rice teaches you the moving parts and Gregg teaches you what to do with them.
-
-## The whole thing as a tape pipeline
-
-The demo isn't a screencast I sat through. It's 14 VHS tapes that drive the TUI deterministically, with a background workload generator producing real syscall traffic for the trace to chew on. One `mage demo` and every GIF below regenerates from scratch. The boring part of "make a demo" — having to re-record everything when the UI shifts — goes away.
-
 ## First launch
 
 ```sh
@@ -132,7 +48,7 @@ You land on the PID picker. The default selection is "All PIDs", so Enter just d
 
 [![Cold start: PID picker, then the dashboard](./unveiling-ior-ng/01-launch.gif "Cold start: PID picker, then the dashboard")](./unveiling-ior-ng/01-launch.gif)  
 
-The dashboard opens on the live flamegraph. Bars grow as new events arrive. Before walking through the keys, a paragraph on what you're looking at — flamegraphs are easier to read than they are to describe.
+The dashboard opens on the live flamegraph. Bars grow as new events arrive. Before walking through the keys, a paragraph on what you're looking at — flamegraphs are easier to read than they are to describe:
 
 A flamegraph is a histogram of stacks. Each horizontal bar is one entry in a stack; every bar directly above it is a child of that entry, and the stack you read top-to-bottom is the same shape as a call chain. In ior, "stack" doesn't mean function-call stack (we don't have userspace symbols). It means a tuple of dimensions of the trace: by default `comm/path/tracepoint`, so the bottom row is per-process names, the middle row is per-file paths, and the top row is the syscall (`enter_read`, `enter_openat`, etc.). A wide bar means lots of events landed in that bucket, a narrow bar means few. There is no time axis — left-to-right is just sort order, not chronology. The whole chart is one "where is the I/O coming from?" picture.
 
@@ -151,15 +67,33 @@ Useful workflows you can do entirely from this tab:
 
 Now the keys. Movement uses vi-style `h`/`j`/`k`/`l` everywhere in ior — and the cursor keys work too if you'd rather. `h`/`l` (or `←`/`→`) walk siblings at the current depth, `j`/`k` (or `↓`/`↑`) step shallower or deeper. `enter` zooms into the selected subtree (the rest of the chart greys out and the selection becomes the new root). `u` or `Esc` undoes the zoom. `b` toggles the metric driving bar width between event count and total bytes. `/` opens regex search; matching frames stay coloured while everything else greys out, so you can use it as a filter as well as a finder. And `o` cycles between five different stack-ordering modes, each with its own lens on the data.
 
-The five orderings ship as built-in presets. The leftmost dimension is the bottom row of the chart (the root); the rightmost is the top row (the leaf). Pressing `o` rotates through them in this order:
+The five orderings ship as built-in presets. Read each preset name as bottom→top: the leftmost dimension is what you'll see lined up across the bottom of the chart (the root row), the next one up is its children, and the rightmost is the top row (the leaf). Switching the order changes which dimension you're scanning first when your eye starts at the bottom.
+
+You change ordering with the `o` hotkey, on the fly, while the trace is still running. No restart, no reset, no re-recording — `o` just rebuilds the live chart with the next preset and keeps streaming new events into it. Press it once to flip from "processes at the bottom" to "paths at the bottom" the moment you realise you'd rather slice the data the other way; press it again to keep cycling. The toolbar updates immediately to show the new `o:order(...)` value. Pressing `o` rotates through the presets in this order:
 
-* `comm/tracepoint/path` — the default. Root rows are processes (by command name); each process's bar splits into the syscalls it issued, and each syscall splits further by file path. Best general-purpose view: "which programs are doing the I/O, and what kind?"
-* `path/tracepoint/comm` — root by file path. Use this when you suspect a particular file or directory is the bottleneck — pick the path, see which syscalls hit it, and which processes did those syscalls. Pairs naturally with directory grouping in the Files tab.
-* `tracepoint/comm/path` — root by syscall. When you already know "this is an `openat` problem" or "we're write-bound", this view collects all the openat (or write) traffic at the bottom and lets you drill into who's doing it and to which paths.
-* `pid/tracepoint/path` — root by PID, not comm. Same shape as the default but each individual process gets its own bar instead of being lumped in with siblings sharing a comm. Useful when you have many bash or python instances and need to tell them apart.
-* `comm/path/tracepoint` — root by process, then by file (skipping the syscall layer at the top). Best when you care about "what files does this program touch?" more than "what syscalls does it issue?" — the file column gets a full row of vertical real estate instead of being split per-syscall.
+Concrete screenshots of each preset on the same workload follow each description, so you can see how the same trace data reshapes itself depending on the lens.
 
-In all five orderings, bar widths still mean the same thing — proportion of the active metric (events or bytes, toggled with `b`). The toolbar at the top of the chart always shows the current ordering as `o:order(<dim1>/<dim2>/<dim3>)`, so you never lose track of which lens you're looking through.
+`comm/tracepoint/path` (default) — processes at the bottom, syscalls in the middle, file paths on top. Each comm bar at the root splits into the syscalls it issued, and each syscall splits further into the files it touched. Best general-purpose view: "which programs are doing the I/O, and what kind?"
+
+[![Ordering 1: comm/tracepoint/path — processes at the bottom (cos…, find, head, notify-rs i…, sh, sqlx-sqlite, xar)](./unveiling-ior-ng/13a-order-by-process.png "Ordering 1: comm/tracepoint/path — processes at the bottom (cos…, find, head, notify-rs i…, sh, sqlx-sqlite, xar)")](./unveiling-ior-ng/13a-order-by-process.png)  
+
+`path/tracepoint/comm` — file paths at the bottom, syscalls in the middle, processes on top. Use this when you suspect a particular file or directory is hot — pick the path, see which syscalls hit it, and which processes did those syscalls. Pairs naturally with directory grouping in the Files tab.
+
+[![Ordering 2: path/tracepoint/comm — file paths at the bottom (/null, /etc/home, /lib64, /tmp, /usr, /share, /paul, /libc, …)](./unveiling-ior-ng/13b-order-by-path.png "Ordering 2: path/tracepoint/comm — file paths at the bottom (/null, /etc/home, /lib64, /tmp, /usr, /share, /paul, /libc, …)")](./unveiling-ior-ng/13b-order-by-path.png)  
+
+`tracepoint/comm/path` — syscalls at the bottom, processes in the middle, file paths on top. When you already know "this is an `openat` problem" or "we're write-bound", this view collects all the openat (or write) traffic into one bar at the root and lets you drill into who's doing it and to which paths.
+
+[![Ordering 3: tracepoint/comm/path — syscalls at the bottom (enter_close, enter_fcntl, enter_mmap, enter_newfstatat, enter_openat, enter_read, …)](./unveiling-ior-ng/13c-order-by-syscall.png "Ordering 3: tracepoint/comm/path — syscalls at the bottom (enter_close, enter_fcntl, enter_mmap, enter_newfstatat, enter_openat, enter_read, …)")](./unveiling-ior-ng/13c-order-by-syscall.png)  
+
+`pid/tracepoint/path` — PIDs at the bottom, syscalls in the middle, file paths on top. Same shape as the default but each individual process gets its own root bar instead of being lumped in with siblings sharing a comm. Useful when you have many bash or python instances and need to tell them apart by ID.
+
+[![Ordering 4: pid/tracepoint/path — PIDs at the bottom (103…, 1…, 1338410, 4113, 4263514, 7709, 8272, …)](./unveiling-ior-ng/13d-order-by-pid.png "Ordering 4: pid/tracepoint/path — PIDs at the bottom (103…, 1…, 1338410, 4113, 4263514, 7709, 8272, …)")](./unveiling-ior-ng/13d-order-by-pid.png)  
+
+`comm/path/tracepoint` — processes at the bottom, file paths in the middle, syscalls on top. Inverse of the default in the upper two layers: you see processes, then which files they hit, then which syscalls hit each file. Best when you care about "what files does this program touch?" more than "what syscalls does it issue?".
+
+[![Ordering 5: comm/path/tracepoint — processes at the bottom, file paths layered above instead of syscalls](./unveiling-ior-ng/13e-order-by-process-paths.png "Ordering 5: comm/path/tracepoint — processes at the bottom, file paths layered above instead of syscalls")](./unveiling-ior-ng/13e-order-by-process-paths.png)  
+
+In every ordering the rule is the same: scan the bottom row to pick a "by what?" dimension, then walk up to drill in. Bar widths always mean the same thing — proportion of the active metric (events or bytes, toggled with `b`). The toolbar at the top of the chart always shows the current ordering as `o:order(<dim1>/<dim2>/<dim3>)`, so you never lose track of which lens you're looking through.
 
 [![Live in-TUI flamegraph: navigate, zoom, undo, cycle order + metric](./unveiling-ior-ng/13-tui-flamegraph.gif "Live in-TUI flamegraph: navigate, zoom, undo, cycle order + metric")](./unveiling-ior-ng/13-tui-flamegraph.gif)  
 
@@ -256,80 +190,13 @@ Three persistence flows, each for a different job:
 
 [![All three headless flows in one tape](./unveiling-ior-ng/14-headless-modes.gif "All three headless flows in one tape")](./unveiling-ior-ng/14-headless-modes.gif)  
 
-## Querying a parquet trace with ClickHouse
+Once a parquet file is on disk, point any SQL-over-parquet tool at it — Part 3 walks through ClickHouse Local, with real query output against a 30-second capture.
 
-The schema is flat and stable: `seq, time_ns, gap_ns, latency_ns, comm, pid, tid, syscall, fd, ret, bytes, file, is_error, filter_epoch`. ClickHouse Local reads parquet directly without a server, which makes it a perfect post-mortem tool — point it at the file and run SQL:
+## Installing it
 
-```sh
-clickhouse local --query "
-  SELECT comm, syscall, count() AS n,
-         formatReadableSize(sum(bytes)) AS total
-  FROM file('trace.parquet', Parquet)
-  GROUP BY comm, syscall
-  ORDER BY n DESC
-  LIMIT 10
-" --format PrettyCompactNoEscapes
-```
-
-```
-    ┌─comm────────────┬─syscall─┬─────n─┬─total──────┐
- 1. │ notify-rs inoti │ read    │ 42005 │ 732.31 KiB │
- 2. │ cosmic-term     │ statx   │ 10898 │ 0.00 B     │
- 3. │ cosmic-term     │ read    │ 10103 │ 4.02 MiB   │
- 4. │ surface-eDP-1   │ ioctl   │  8452 │ 0.00 B     │
- 5. │ cosmic-term     │ close   │  4918 │ 0.00 B     │
- 6. │ cosmic-term     │ openat  │  4537 │ 0.00 B     │
- 7. │ cosmic-term     │ ioctl   │  3556 │ 0.00 B     │
- 8. │ tokio-runtime-w │ read    │  1976 │ 4.04 MiB   │
- 9. │ cosmic-comp     │ read    │  1118 │ 6.63 KiB   │
-10. │ systemd-oomd    │ read    │  1085 │ 111.97 KiB │
-    └─────────────────┴─────────┴───────┴────────────┘
-```
+The Rocky Linux 9 install procedure (with its kernel-backport caveat), the eBPF / CO-RE / static-linking explanation that makes the resulting binary "compile once, run everywhere", and the build host vs. trace host split all live in Part 2. The short version: you only have to build it once. The 23 MB binary then `scp`s to anywhere.
 
-The fields you actually want for performance work are `latency_ns` and `gap_ns`. P99 by syscall, only the ones that landed in error:
-
-```sh
-clickhouse local --query "
-  SELECT syscall, count() AS n,
-         round(quantile(0.5)(latency_ns)/1000,  1) AS p50_us,
-         round(quantile(0.99)(latency_ns)/1000, 1) AS p99_us
-  FROM file('trace.parquet', Parquet)
-  WHERE is_error = 1
-  GROUP BY syscall
-  ORDER BY p99_us DESC
-" --format PrettyCompactNoEscapes
-```
-
-```
-    ┌─syscall────┬─────n─┬─p50_us─┬─p99_us─┐
- 1. │ statx      │  1216 │    2.2 │   16.4 │
- 2. │ newfstatat │    69 │    1.7 │   16.4 │
- 3. │ open       │     1 │   16.1 │   16.1 │
- 4. │ mkdir      │   306 │    3.9 │   11.7 │
- 5. │ readlink   │    11 │    1.5 │   10.4 │
- 6. │ newstat    │    44 │    2.5 │    8.4 │
- 7. │ unlinkat   │   347 │      1 │    6.2 │
- 8. │ openat     │   380 │    2.1 │    5.8 │
- 9. │ access     │     2 │      5 │    5.5 │
-10. │ read       │ 23597 │    0.5 │    5.4 │
-11. │ ioctl      │   901 │      1 │    5.3 │
-12. │ writev     │     1 │    0.7 │    0.7 │
-    └────────────┴───────┴────────┴────────┘
-```
-
-Real output, by the way — those rows are from a 30-second `ior -parquet trace.parquet` capture on the laptop I'm typing this on. `notify-rs inoti…` is the inotify thread of some Rust app I had open; `cosmic-term` is the COSMIC desktop's terminal emulator. The slowest p99 errors are the directory-walking syscalls (statx, newfstatat, mkdir) at ~16 µs — bog standard.
-
-Same trick works in DuckDB (`duckdb -c "SELECT ... FROM 'trace.parquet'"`), pandas, polars, anything that reads Parquet. The point of streaming Parquet rather than ior's native `.ior.zst` format is exactly this: once it's on disk, you're in the standard data-tools ecosystem.
-
-## Reproducing the whole demo
-
-```sh
-mage installDemoTools     # one-time: VHS via go install + ttyd from dnf
-sudo -v                   # warm the sudo timestamp once
-mage demo                 # ~10 minutes, fully headless, safe to background
-```
-
-To rebuild a single GIF after editing its tape: `TAPE=07-stream-live mage demoOne`.
+[Part 2: install + compile once, run everywhere](./DRAFT-unveiling-ior-ng-part-2.md)  
 
 ## What's still missing
 
@@ -341,5 +208,9 @@ ior is pre-alpha and basically a personal tool. The headline gaps:
 
 But the live flamegraph, the stackable stream filters, and the cheap parquet capture together cover the cases I actually hit week to week. The demo above is the easiest way to get a feel for whether it's the kind of tool you want.
 
+For installing it and the eBPF / CO-RE / static-linking story (why one build runs on every other Linux box you scp it to), see Part 2. For the per-event schema, async-syscall caveats, the probe-generator safeguard against missing new kernel syscalls, and post-mortem SQL on the parquet output, see Part 3.
+
+[Part 2: install + compile once, run everywhere](./DRAFT-unveiling-ior-ng-part-2.md)  
+[Part 3: under the hood (schema, probe generator, ClickHouse)](./DRAFT-unveiling-ior-ng-part-3.md)  
 [Source on Codeberg](https://codeberg.org/snonux/ior)  
 [The full in-repo tutorial](https://codeberg.org/snonux/ior/src/branch/main/demo/TUTORIAL.md)  
diff --git a/gemfeed/DRAFT-unveiling-ior-ng-part-2.md b/gemfeed/DRAFT-unveiling-ior-ng-part-2.md
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@@ -0,0 +1,214 @@
+# Unveiling I/O Riot NG — Part 2: install and compile once, run everywhere
+
+> Draft — not in the gemfeed yet. Promote with the usual rename + index dance.
+
+This is Part 2 of three. Part 1 is the demo-driven tour — what ior looks like, how the dashboard tabs work, how filtering and recording behave. This part is about the install dance for Rocky Linux 9 (with one annoying kernel-backport caveat) and, more interestingly, why you only have to do that dance on a single machine: the resulting binary is portable to every other Linux box thanks to CO-RE — Compile Once, Run Everywhere — plus full static linking. Part 3 is the under-the-hood companion (per-event schema, async-syscall caveats, the syscall-coverage probe generator, and post-mortem SQL on the parquet output).
+
+If you came here for the dashboard tour, that's Part 1. If you want to know how the data pipeline is shaped after you've got ior running, that's Part 3. This one is for the moment between "I want to try this" and "OK, it's running on the box I care about."
+
+[Part 1: a guided tour](./DRAFT-unveiling-ior-ng-part-1.md)  
+[Part 3: under the hood (schema, probe generator, ClickHouse)](./DRAFT-unveiling-ior-ng-part-3.md)  
+[I/O Riot NG on Codeberg](https://codeberg.org/snonux/ior)  
+[the original I/O Riot post (2018)](./2018-06-01-realistic-load-testing-with-ioriot-for-linux.md)  
+
+[![I/O Riot NG logo](./unveiling-ior-ng/00-logo.png "I/O Riot NG logo")](./unveiling-ior-ng/00-logo.png)  
+
+
+## Table of Contents
+
+* [⇢ Unveiling I/O Riot NG — Part 2: install and compile once, run everywhere](#unveiling-io-riot-ng--part-2-install-and-compile-once-run-everywhere)
+* [⇢ ⇢ Installing ior](#installing-ior)
+* [⇢ ⇢ ⇢ Why native installation is a mess](#why-native-installation-is-a-mess)
+* [⇢ ⇢ ⇢ What the Docker build is actually doing](#what-the-docker-build-is-actually-doing)
+* [⇢ ⇢ A short detour: eBPF and libbpfgo](#a-short-detour-ebpf-and-libbpfgo)
+* [⇢ ⇢ CO-RE — the part that makes the binary actually portable](#co-re--the-part-that-makes-the-binary-actually-portable)
+* [⇢ ⇢ A note on cgo overhead](#a-note-on-cgo-overhead)
+* [⇢ ⇢ If you want to go deeper](#if-you-want-to-go-deeper)
+* [⇢ ⇢ Wrapping up](#wrapping-up)
+
+## Installing ior
+
+The short answer: use Docker. One command, no toolchain setup, works from any Docker-capable Linux host with BTF available:
+
+```sh
+git clone https://codeberg.org/snonux/ior ~/git/ior
+cd ~/git/ior
+mage buildDocker
+```
+
+First run builds a Rocky Linux 9 builder image (~15–20 minutes). Subsequent runs reuse the cached image and finish in under a minute. The resulting static binary lands at `./ior`.
+
+That's the officially supported install path, and it's the right one for anyone who just wants to run ior without living in its build system.
+
+### Why native installation is a mess
+
+If you're curious why Docker became the answer, the native install on Rocky Linux 9 illustrates the problem well. Three separate things bite you before you even get to `mage build`:
+
+Rocky 9 ships neither `libelf.a` nor `libzstd.a` — there are no `*-static` subpackages for either, only the dynamic `.so` files. Both have to be compiled from source. `libelf` from the elfutils source RPM, `libzstd` from the upstream GitHub release tarball.
+
+Rocky 9 also only ships Go 1.25.x, but ior requires 1.26+. So Go itself has to be installed from go.dev in parallel with the library builds.
+
+And there's a kernel quirk that used to make this section much longer. Pre-fix, ior would happily load on a stock 5.14 RHEL kernel and then die on the very first tracepoint attach with `BPF_LINK_CREATE`/`BPF_PERF_EVENT` returning `EACCES` — even as root, with SELinux permissive, with every BPF-related sysctl wide open. The cause is that RHEL 9 carries an `rt`-tree backport that adds `preempt_lazy_count` to `struct trace_entry`. That widens the BTF-emitted alias `trace_event_raw_sys_enter`/`_exit` by 8 bytes and shifts the `args`/`ret` offsets — but the actual context the kernel hands the BPF program is still `struct syscall_trace_enter`/`_exit`, where the offsets did not move. Programs written against `trace_event_raw_sys_*` (the conventional choice; bcc, libbpf-tools, and ior all used to do this) end up reading past `max_ctx_offset`, so the verifier rejects the attach. The fix — also what bcc shipped in [PR #4920](https://github.com/iovisor/bcc/pull/4920) and what inspektor-gadget did — is to type the BPF context as `syscall_trace_enter`/`_exit` directly. ior now generates its handlers that way, and stock 5.14 RHEL/Rocky/Alma works without an ElRepo kernel.
+
+### What the Docker build is actually doing
+
+The Dockerfile encodes exactly the same steps that a native install on Rocky 9 would require. Here is the full sequence so you have a mental model of what's inside the image, and so you could reproduce it on a bare host if you ever needed to:
+
+```sh
+# 1) Enable repos and install build dependencies. CRB ships zlib-static / glibc-static.
+sudo dnf config-manager --set-enabled crb
+sudo dnf install -y epel-release
+sudo dnf install -y gcc clang bpftool elfutils-libelf-devel zlib-static \
+    glibc-static libzstd-devel git make cmake wget rpmdevtools strace bpftrace
+sudo dnf builddep -y elfutils
+
+# 2) Install Go 1.26 from go.dev. Rocky 9 ships only Go 1.25.x, ior needs 1.26+.
+cd /tmp
+wget -q https://go.dev/dl/go1.26.2.linux-amd64.tar.gz
+sudo tar -C /usr/local -xf go1.26.2.linux-amd64.tar.gz
+echo 'export PATH=/usr/local/go/bin:$HOME/go/bin:$PATH' | sudo tee /etc/profile.d/go.sh
+source /etc/profile.d/go.sh
+
+# 3) Build libelf.a from the elfutils source RPM.
+mkdir -p ~/src && cd ~
+dnf download --source elfutils-libelf
+rpm -ivh elfutils-*.src.rpm
+tar -C ~/src -xjf rpmbuild/SOURCES/elfutils-*.tar.bz2
+cd ~/src/elfutils-*
+./configure --enable-deterministic-archives --disable-debuginfod --disable-libdebuginfod
+make -C lib -j$(nproc)
+make -C libelf -j$(nproc)
+sudo cp -v libelf/libelf.a /usr/lib64/
+
+# 4) Build libzstd.a from upstream (libzstd-devel doesn't ship the static archive).
+cd /tmp
+wget -q https://github.com/facebook/zstd/releases/download/v1.5.5/zstd-1.5.5.tar.gz
+tar xzf zstd-1.5.5.tar.gz
+make -C zstd-1.5.5/lib -j$(nproc) libzstd.a
+sudo cp -v zstd-1.5.5/lib/libzstd.a /usr/lib64/
+
+# 5) Clone ior + libbpfgo, pin libbpfgo, build the static libbpf archive, install mage.
+mkdir -p ~/git
+git clone https://codeberg.org/snonux/ior ~/git/ior
+git clone https://github.com/aquasecurity/libbpfgo ~/git/libbpfgo
+git -C ~/git/libbpfgo checkout v0.9.2-libbpf-1.5.1
+git -C ~/git/libbpfgo submodule update --init --recursive
+make -C ~/git/libbpfgo libbpfgo-static
+go install github.com/magefile/mage@latest
+
+# 6) Generate the syscall-coverage handlers against THIS kernel and build.
+# IOR_FORCE_GENERATE bypasses the strict diff against the committed audit file
+# (the committed audit was generated against a different kernel build, and the
+# generator's safeguard would otherwise refuse to overwrite it).
+cd ~/git/ior
+env IOR_FORCE_GENERATE=1 GOTOOLCHAIN=auto mage generate
+env GOTOOLCHAIN=auto mage all
+
+# 7) Smoke test.
+sudo ./ior -plain -duration 5
+```
+
+If you see `Probing for 5s` followed by CSV rows, the build is good. `mage buildDocker` runs all of this inside a container and hands you back just the final binary — the 15-minute first-run cost buys you never having to think about any of the above again.
+
+## A short detour: eBPF and libbpfgo
+
+If you haven't touched eBPF before: it's a small in-kernel bytecode VM. You compile a tiny C program, the kernel verifies it can't crash or loop forever, and then it runs every time some hook fires — a syscall enter/exit, a kprobe, a tracepoint, a network packet. The program writes events into a ring buffer that userspace mmaps and drains. No kernel module, no patched kernel, no debug symbols required.
+
+ior plugs into the syscall tracepoints — `sys_enter_openat`, `sys_exit_read`, etc. — and the BPF side does the bare minimum: timestamp the event, copy a few fields, push to a perf ring buffer. All the heavy lifting (string interning, latency math, aggregation, the dashboard) is in Go on the userspace side.
+
+The kernel ships a C library called libbpf that handles loading the program, attaching it to hooks, managing maps, and reading the ring buffer. There are two well-known ways to drive that from Go:
+
+* libbpfgo (Aqua Security): a thin cgo wrapper around libbpf. You ship libbpf along with your binary and call into the same C API that `bpftool` and `perf` use.
+* cilium/ebpf: a from-scratch pure-Go reimplementation of everything libbpf does — ELF parser, BTF resolver, syscall layer, the lot.
+
+I went with libbpfgo specifically because it's a wrapper, not a reimplementation. Whatever lands in libbpf upstream — new map types, new attach kinds, CO-RE fixes — I get for free the next kernel cycle. The pure-Go variant has to chase libbpf's feature set in parallel, and any divergence is on me to debug. For a tracer that's mostly value-add on the userspace side, "be a thin client of the kernel's own library" wins.
+
+## CO-RE — the part that makes the binary actually portable
+
+The headline fact about ior's deployment story: build it once on one box, then `scp ior other-host:/usr/local/bin/` to anywhere else and it just runs. No recompile per kernel, no kernel-debuginfo dance, no DKMS hooks. Two mechanisms make that work, and they reinforce each other.
+
+The first is plain old static linking on the userspace side. A quick refresher on what that means, since it's central to why "scp the binary anywhere" works: when you build a normal Linux executable, the linker has two ways to wire library code into your program. Dynamic linking ("shared library") leaves a placeholder in the binary that says "at run time, find `libfoo.so.6` somewhere on `LD_LIBRARY_PATH` and pull in its symbols." Static linking pastes the library's machine code directly into your binary at build time, so there's nothing to look up later. Dynamic is smaller on disk and lets distros patch shared libs without rebuilding everything; static is bigger but self-contained — no surprise about which version of the library the target box happens to have, no `error while loading shared libraries: libwhatever.so.6: cannot open shared object file` when the target ships a newer ABI.
+
+For Go, this is mostly a non-issue. A pure-Go binary (no cgo) is statically linked by default — the Go toolchain produces a single self-contained ELF file with no `.dynamic` section and no `NEEDED` entries. You can `scp` it to any Linux box of the same architecture and it just runs. That's one of the quietly nice things about Go.
+
+ior is the not-quite-pure case: it goes through cgo to call into libbpf, libelf, and libzstd, and each of those has its own .so on the build host. By default cgo links those C dependencies dynamically, which would defeat the "scp the binary anywhere" property — the target box would need to have matching `.so` files at matching versions, which is exactly the kind of dependency hell Go usually saves you from. The fix is the line `-extldflags "-static"` in ior's Magefile: it tells the external (C) linker to resolve `-lbpf -lelf -lzstd -lz` against the static archives (`.a` files) instead of the dynamic ones. That's why the install procedure above is so picky about having `libelf.a` and `libzstd.a` actually present on the build host — without them the C-side static link fails outright.
+
+The result is a single ~23 MB binary with libbpf, libelf, libzstd, and zlib all baked in. None of them are looked up dynamically at runtime. The build host's library versions stay on the build host. (A couple of glibc resolver functions — `getpwnam_r` and friends — do still fall back to the target's libc, which is fine on any reasonable distro and is what the linker warnings during the build are about.)
+
+The second, and the one that's actually unusual, is CO-RE — Compile Once, Run Everywhere. CO-RE is the eBPF feature that solves the "the kernel changed its struct layout between releases" problem.
+
+The old I/O Riot was Systemtap. Systemtap programs are translated into a kernel module against the running kernel's exact headers, and that module then has to be loaded with `insmod`. That meant: the user has to install a kernel-debuginfo package matching their running kernel, and a fresh build per host (or per kernel update). On the BSD-style "you only run what you compiled here" laptop crowd that was tolerable; on a fleet of distros + kernel versions it was a recurring tax. Half of the original I/O Riot's README was about kernel-debuginfo dance steps.
+
+CO-RE throws all of that out. The idea, in one paragraph: when you write a BPF program that reads `task->mm->start_stack`, you don't bake the offsets of those fields into the compiled program. Instead, the compiler emits relocation records ("at this instruction, fetch the offset of `mm` inside `task_struct`"). At load time, libbpf looks up the actual offsets in the target kernel's BTF (BPF Type Format — a description of every kernel struct, embedded in `/sys/kernel/btf/vmlinux` on any modern kernel) and patches the program in place. The same `.bpf.o` that ran on a 5.10 Debian kernel runs on a 6.8 Fedora kernel without recompilation.
+
+Pictorially, the contrast looks like this:
+
+```
+Old I/O Riot (Systemtap)                 New ior (libbpf + CO-RE)
+─────────────────────────                ────────────────────────────
+  .stp source                              .bpf.c source
+       │                                        │
+       │ needs THIS kernel's headers            │ build ONCE against vmlinux.h
+       │ + debuginfo package installed          │ (generated from any kernel BTF)
+       ▼                                        ▼
+  per-host translate + compile              one portable .bpf.o
+       │                                        │
+       ▼                                        ▼
+  per-host kernel module                    same binary on every host
+       │                                        │
+  insmod / modprobe                         libbpf loader:
+       │                                        │  • read /sys/kernel/btf/vmlinux
+       ▼                                        │  • patch field offsets
+  attached, this kernel only                 │  • verify + load
+                                              ▼
+                                          attached, runs anywhere
+```
+
+What that buys ior in practice: I ship a single `ior` binary. On any Linux ≥4.18-ish with BTF available (which is almost all of them now — Debian, Ubuntu, Fedora, Arch, RHEL, and ElRepo's `kernel-ml` builds all ship `CONFIG_DEBUG_INFO_BTF=y` by default), it just works. No kernel-debuginfo dependency, no per-kernel build matrix, no DKMS hooks. The first time I tried `scp ior fedora-box:` and it ran without complaint after a 6-month gap I had to double-check it wasn't silently doing nothing.
+
+So the operational shape is: pick one box, do the install dance from the Rocky section above (or the Fedora one in the README) once, build, then distribute the 23 MB binary wherever you want to trace. The build host needs Go and clang and the static libraries. The trace hosts need a BTF-enabled kernel and `sudo`. That's it.
+
+The runtime shape of a trace pipeline lines up with that:
+
+```
+ kernel side                                userspace (this binary)
+ ───────────                                ───────────────────────
+                                            ┌──────────────────────┐
+   tracepoint:                              │  Go process          │
+   sys_enter_openat                         │  ┌────────────────┐  │
+        │                                   │  │  aggregator    │  │
+        ▼                                   │  │  (latency,     │  │
+   ┌─────────┐                              │  │   stacks,      │  │
+   │ BPF prog│ ─── perf ring buf ──────────>│──│   filters)     │  │
+   │ (verified                              │  └─────┬──────────┘  │
+   │  bytecode)                             │        │             │
+   └─────────┘                              │        ▼             │
+                                            │  Bubble Tea TUI /    │