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| author | Paul Buetow <paul@buetow.org> | 2026-05-07 10:01:05 +0300 |
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| committer | Paul Buetow <paul@buetow.org> | 2026-05-07 10:01:05 +0300 |
| commit | 47294db3a7ab4cfca4c0eb2674556400592af083 (patch) | |
| tree | ab82b1d4aae0c1310330bb7787871ce94fe3a415 | |
| parent | 58ba502a0580d2fcb3a8198f7ef9e21da7aecc03 (diff) | |
Update content for md
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| -rw-r--r-- | gemfeed/DRAFT-ior-guided-tour.md | 213 | ||||
| -rw-r--r-- | gemfeed/DRAFT-unveiling-ior-ng-part-2.md | 35 | ||||
| -rw-r--r-- | gemfeed/DRAFT-unveiling-ior-ng-part-3.md | 64 | ||||
| -rw-r--r-- | gemfeed/index.md | 1 | ||||
| -rw-r--r-- | gemfeed/unveiling-ior-ng/00-logo.png | bin | 332693 -> 28775 bytes | |||
| -rw-r--r-- | index.md | 3 | ||||
| -rw-r--r-- | uptime-stats.md | 24 |
8 files changed, 115 insertions, 311 deletions
diff --git a/gemfeed/DRAFT-unveiling-ior-ng-part-1.md b/gemfeed/2026-05-08-unveiling-ior-ng-part-1.md index 6f0aaf10..2ffb50e0 100644 --- a/gemfeed/DRAFT-unveiling-ior-ng-part-1.md +++ b/gemfeed/2026-05-08-unveiling-ior-ng-part-1.md @@ -1,20 +1,21 @@ -# Unveiling I/O Riot NG — Part 1: a guided tour +# Unveiling I/O Riot NG 1.0.0 — Part 1: a guided tour -> Draft — not in the gemfeed yet. Promote with the usual rename + index dance. +> Published at 2026-05-07T09:46:29+03:00 -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. +I rewrote I/O Riot. The old version, written in C and SystemTap, dates back to 2017. The new version (called `ior`) uses Go, C, and BPF via libbpfgo. It runs on Linux and is primarily a TUI dashboard rather than a record/replay box. It took around two years of intermittent work to reach this `1.0.0` release. -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. +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. -[](./unveiling-ior-ng/00-hero-flamegraph.png) +[](./unveiling-ior-ng/00-hero-flamegraph.png) +[2026-05-08 Unveiling I/O Riot NG 1.0.0 — Part 1: a guided tour (You are currently reading this)](./2026-05-08-unveiling-ior-ng-part-1.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) ## Table of Contents -* [⇢ Unveiling I/O Riot NG — Part 1: a guided tour](#unveiling-io-riot-ng--part-1-a-guided-tour) +* [⇢ Unveiling I/O Riot NG 1.0.0 — Part 1: a guided tour](#unveiling-io-riot-ng-100--part-1-a-guided-tour) * [⇢ ⇢ What it does](#what-it-does) * [⇢ ⇢ First launch](#first-launch) * [⇢ ⇢ The seven tabs, in 30 seconds each](#the-seven-tabs-in-30-seconds-each) @@ -27,12 +28,11 @@ This is the first of three posts. Part 1 is the demo-driven tour: what ior looks * [⇢ ⇢ The Stream tab is the good one](#the-stream-tab-is-the-good-one) * [⇢ ⇢ Filtering, more thoroughly](#filtering-more-thoroughly) * [⇢ ⇢ Recording](#recording) -* [⇢ ⇢ 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 — 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. +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. @@ -48,24 +48,24 @@ You land on the PID picker. The default selection is "All PIDs", so Enter just d [](./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, since 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. +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 [yet]). 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's 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. -One thing worth flagging because it's the unusual bit: this flamegraph is live. Most of the flamegraph tooling out there — Brendan Gregg's `flamegraph.pl`, all the `perf script | stackcollapse-* | flamegraph.pl` pipelines, every `pprof -web` invocation — produces a static SVG: capture a profile for N seconds, render once, browse the result. ior's tab is not that. Bars grow, shrink, appear, and disappear in real time as events stream in from the kernel — at full screen-refresh rate while the workload runs, with no pause. You can sit on this tab while you change something on the system (start a build, cycle a service, run a query) and watch the I/O shape mutate underneath you. That's a different mental model from the static "I have a profile, let me look at it" workflow most people are used to, and it's what makes the tab actually useful as an at-a-glance diagnostic surface rather than a post-mortem artifact. +The unusual bit: this flamegraph is live. Most of the flamegraph tooling out there (Brendan Gregg's `flamegraph.pl`, all the `perf script | stackcollapse-* | flamegraph.pl` pipelines, every `pprof -web` invocation) produces a static SVG: capture a profile for N seconds, render once, browse the result. `ior`'s tab is not that. Bars grow, shrink, appear, and disappear in real time as events stream in from the kernel, at full screen-refresh rate while the workload runs, with no pause. You can sit on this tab while you change something on the system (start a build, cycle a service, run a query) and watch the I/O shape mutate underneath you. That's a different mental model from the static "I have a profile, let me look at it" workflow most people are used to, and it's what makes the tab actually useful as an at-a-glance diagnostic surface rather than a post-mortem artifact. -Because it's live, there's also a way to throw away the accumulated history and start the rolling count from "now": `r` resets the baseline. Everything the flamegraph has been counting since launch (or since the last reset) is dropped, and from that moment the chart reflects only events that arrived after the reset. Useful for the "compare before vs after" workflow — change one thing on the box, hit `r` immediately, and the next thirty seconds of accumulation is a fresh picture of the new state. +Because it's live, there's also a way to throw away the accumulated history and start the rolling count from "now": `r` resets the baseline. Everything the flamegraph has been counting since launch (or since the last reset) is dropped, and from that moment the chart reflects only events that arrived after the reset. Useful for the "compare before vs after" workflow — change one thing on the box, hit `r` immediately, and the next thirty seconds of accumulation is a fresh picture of the new state. You can also pause (and resume) the flame graph (with the `space` key) to get the static picture. -That visualisation buys you two things you can't easily get from a tabular view. First, hierarchy: it's immediately obvious whether one process is responsible for ten thousand reads on a single file, or ten thousand reads spread across a hundred files — the first looks like one tall pillar, the second looks like a wide ridge. Second, scale: bar width is proportional to the metric (count or bytes), so a process that did 95% of the work towers over the others. The eye picks that up instantly; the same fact in a sorted table requires reading numbers and doing the ratio mentally. +That visualisation buys you two things you can't easily get from a tabular view. First, hierarchy: it's obvious whether one process is doing ten thousand reads on a single file, or ten thousand reads spread across a hundred files. The first looks like one tall pillar, the second looks like a wide ridge. Second, scale: bar width is proportional to the metric (count or bytes), so a process that did 95% of the work towers over the others. The eye picks that up instantly. The same fact in a sorted table needs you to read numbers and do the ratio in your head. Useful workflows you can do entirely from this tab: -* "What's pounding the disk?" — leave it on default order (`comm/path/tracepoint`) and watch which `comm` widens. Press `b` once to switch the metric to bytes if you care about throughput, not call count. -* "Why is this one process slow?" — `l` (or `→`) until the cursor is on that process, then `enter` to zoom. The whole chart re-roots there and you see only that process's paths and syscalls. -* "What's in /var/lib/X?" — press `o` once to flip ordering to `path/tracepoint/comm`, navigate to the path, zoom. Now the children show which syscalls hit it and which processes did them. -* "Did the new deploy change the I/O shape?" — press `r` to reset the baseline, wait a bit, and the chart starts fresh with only events from the reset point onward. Pair the same syscall surface "before" vs "after" and the difference jumps out by shape. +* "What's pounding the disk?" Leave it on default order (`comm/path/tracepoint`) and watch which `comm` widens. Press `b` once to switch the metric to bytes if you care about throughput, not call count. +* "Why is this one process slow?" `l` (or `→`) until the cursor is on that process, then `enter` to zoom. The whole chart re-roots there and you see only that process's paths and syscalls. +* "What's in /var/lib/X?" Press `o` once to flip ordering to `path/tracepoint/comm`, navigate to the path, zoom. Now the children show which syscalls hit it and which processes did them. +* "Did the new deploy change the I/O shape?" Press `r` to reset the baseline, wait a bit, and the chart starts fresh with only events from the reset point onward. Pair the same syscall surface "before" vs "after" and the difference jumps out by shape. -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. +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. `o` cycles between five different stack-ordering modes, each with its own lens on the data. `H` toggles a built-in help panel showing every key the current tab responds to, which is the easiest way to discover what's bound where without leaving the dashboard. 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. @@ -93,7 +93,9 @@ Concrete screenshots of each preset on the same workload follow each description [](./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. +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. + +If you want to skip the rotate-with-`o` dance and pick a custom three-tuple from the start, the headless side has you covered: `-fields comm,tracepoint,path` (or any other valid combination of `comm`, `pid`, `tid`, `tracepoint`, `path`) sets the collapse fields up front, and `-count count|bytes` picks the metric. Both are inherited by the live TUI flamegraph if you go that way, and they're what `mage demo` uses when it wants a specific ordering on a specific tape. Useful for scripted captures where you already know the lens you want. [](./unveiling-ior-ng/13-tui-flamegraph.gif) @@ -109,7 +111,7 @@ A sparkline plus the top syscalls and top paths — the at-a-glance view, useful ### `3` Syscalls -A sortable table of every syscall ior knows about, with rate, average latency, p95/p99, total bytes, and error count. `s` sorts by the selected column, `S` reverses. The most useful column when something's wrong is usually p99 — it's where you see the long-tail outlier syscall types. +A sortable table of every syscall `ior` knows about, with rate, average latency, p95/p99, total bytes, and error count. `s` sorts by the selected column, `S` reverses. The most useful column when something's wrong is usually p99 — it's where you see the long-tail outlier syscall types. [](./unveiling-ior-ng/03-syscalls-tab.gif) @@ -129,9 +131,9 @@ Same shape again, but rows are processes / comms. Best paired with the Stream ta Two histograms side by side: how long each syscall took (latency), and the wall-clock interval between syscalls on the same thread (gap). Latency tells you "is the kernel slow"; gap tells you "what is the program doing between two kernel calls". -A subtle but important point about that gap: ior measures it from the exit of one syscall to the entry of the next on the same TID, but it does not know what the thread was doing in the meantime. A long gap doesn't mean the thread was idle — it might have been pinned on a CPU running pure userspace code (number-crunching, JSON parsing, GC, a busy loop). All "gap" tells you for sure is "this thread didn't call into the kernel for X microseconds." Whether that's because it was sleeping, blocked on a condition variable, computing, or scheduled out is something only the gap value alone cannot answer — pair it with `top`/`perf top` if you need to disambiguate. In practice this is still extremely useful: a syscall-driven workload with surprisingly long gaps is a strong hint that you're CPU-bound somewhere outside the kernel, and that's a different optimisation conversation than slow I/O. +One important point about that gap: `ior` measures it from the exit of one syscall to the entry of the next on the same TID, but it doesn't know what the thread was doing in the meantime. A long gap doesn't mean the thread was idle. It might have been pinned on a CPU running pure userspace code (number-crunching, JSON parsing, GC, a busy loop). All "gap" tells you for sure is "this thread didn't call into the kernel for X microseconds." Whether that's because it was sleeping, blocked on a condition variable, computing, or scheduled out is something the gap value alone cannot answer. Pair it with `top`/`perf top` if you need to disambiguate. Still useful in practice: a syscall-driven workload with surprisingly long gaps is a strong hint that you're CPU-bound somewhere outside the kernel, and that's a different optimisation conversation than slow I/O. -The dd loop in the demo workload spreads the latency distribution out so you can actually see the shape. +The `dd` loop in the demo workload spreads the latency distribution out so you can actually see the shape. [](./unveiling-ior-ng/06-latency-gaps-tab.gif) @@ -143,7 +145,7 @@ The live tail — every event as it happens, in a row-per-event ring buffer. Thi ## The Stream tab is the good one -`space` pauses. In pause mode, the same vi-style `h`/`j`/`k`/`l` (or arrow keys) move the row/column cursor across the table. Hitting `Enter` on a cell pushes a new filter onto a stack, narrowing what you see. Pile them up — comm, then syscall, then file — and `Esc` pops them off LIFO when you want to back out. +`space` pauses. In pause mode, the same vi-style `h`/`j`/`k`/`l` (or arrow keys) move the row/column cursor across the table. Hitting `Enter` on a cell pushes a new filter onto a stack, narrowing what you see. Pile them up — comm, then syscall, then file — and `ESC` pops them off LIFO when you want to back out. [](./unveiling-ior-ng/08-stream-pause-filter.gif) @@ -161,13 +163,13 @@ The Enter-to-push trick isn't unique to Stream. It works the same on Files, Sysc The filter status line gives you a one-glance summary of every active frame, written like: -* `comm~bash` — substring match on a string column. This is what Enter-on-a-cell produces for `comm`, `syscall`, and `file`. -* `pid=1234` — exact equality. Used for `pid`, `tid`, `fd`, `ret`, `bytes`. -* `latency>=5ms` / `gap>=10us` — numeric comparison with a duration suffix. The full operator set is `>`, `<`, `=`, `>=`, `<=`, `!=`. +* `comm~bash`: substring match on a string column. This is what Enter-on-a-cell produces for `comm`, `syscall`, and `file`. +* `pid=1234`: exact equality. Used for `pid`, `tid`, `fd`, `ret`, `bytes`. +* `latency>=5ms` / `gap>=10us`: numeric comparison with a duration suffix. The full operator set is `>`, `<`, `=`, `>=`, `<=`, `!=`. Stack frames AND together, so pushing `comm~bash` and then `syscall~openat` shows you bash's openat calls, not bash OR openat. -Undoing is symmetric to pushing: `Esc` pops the most recent frame off the stack — one keystroke per layer, LIFO. Press it once to drop the `syscall~openat` filter and you're back to bash-only; press it again and the `comm~bash` filter goes too, leaving the unfiltered firehose. To clear the whole stack at once, just hold `Esc` until the status line reads `filter: all`. The `F` key is a synonym for `Esc` here and works from any tab — handy from Files/Syscalls/Processes where `Esc` might otherwise close a modal first. +Undoing is symmetric to pushing: `ESC` pops the most recent frame off the stack, one keystroke per layer, LIFO. Press it once to drop the `syscall~openat` filter and you're back to bash-only; press it again and the `comm~bash` filter goes too, leaving the unfiltered view. To clear the whole stack at once, just hold `ESC` until the status line reads `filter: all`. The `F` key is a synonym for `ESC` here and works from any tab, handy from Files/Syscalls/Processes where `ESC` might otherwise close a modal first. Two other knobs do related work: @@ -180,37 +182,35 @@ Two other knobs do related work: Three persistence flows, each for a different job: -* `R` from the dashboard starts streaming Parquet — every event row that survives your current TUI filter goes to disk continuously. `R` again stops. Footer shows the active file or the last error. +* `R` from the dashboard starts streaming Parquet. Every event row that survives your current TUI filter goes to disk continuously. `R` again stops. Footer shows the active file or the last error. If you don't want CSV snapshot exports at all (the `e` / `x` keys), launch with `-tuiExport=false` and those keys go away. [](./unveiling-ior-ng/12-parquet-recording.gif) -* `sudo ./ior -flamegraph -name <n>` writes one aggregated `.ior.zst` artifact at shutdown. Aggregated counters, not per-event rows. Cheaper to write, ideal for ior's native flamegraph workflow and integration tests. +* `sudo ./ior -flamegraph -name <n>` writes one aggregated `.ior.zst` artifact at shutdown. Aggregated counters, not per-event rows. Cheaper to write, ideal for `ior`'s native flamegraph workflow and the integration test harness (which I'll come back to in Part 3). -* `sudo ./ior -parquet trace.parquet` is the headless firehose — every row, no TUI, no filtering. `sudo ./ior -plain` is even lighter: CSV to stdout, pipe it into anything. +* `sudo ./ior -parquet trace.parquet` is the headless firehose: every row, no TUI, no filtering. `sudo ./ior -plain` is even lighter, CSV to stdout, pipe it into anything. [](./unveiling-ior-ng/14-headless-modes.gif) 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. -## Installing it - -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. - -[Part 2: install + compile once, run everywhere](./DRAFT-unveiling-ior-ng-part-2.md) - ## What's still missing -ior is pre-alpha and basically a personal tool. The headline gaps: - -* No record/replay — that was the whole point of the original I/O Riot. The new one is a tracer, not a workload simulator. I keep going back and forth on whether to put replay back in. +* No record/replay. That was the whole point of the original I/O Riot. The new one is a tracer, not a workload simulator. I keep going back and forth on whether to put replay back in. * No userspace symbol resolution. Stacks are at the syscall surface, not "which line of which library called read". -* No remote / cluster mode. Single host, one trace at a time. 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. +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 (once published). 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 (once published.). -[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/docs/tutorial/tutorial.md) + +E-Mail your comments to `paul@nospam.buetow.org` :-) + +Other related posts are: + +[2026-05-08 Unveiling I/O Riot NG 1.0.0 — Part 1: a guided tour (You are currently reading this)](./2026-05-08-unveiling-ior-ng-part-1.md) +[2018-06-01 Realistic load testing with I/O Riot for Linux](./2018-06-01-realistic-load-testing-with-ioriot-for-linux.md) + +[Back to the main site](../) diff --git a/gemfeed/DRAFT-ior-guided-tour.md b/gemfeed/DRAFT-ior-guided-tour.md deleted file mode 100644 index df52e070..00000000 --- a/gemfeed/DRAFT-ior-guided-tour.md +++ /dev/null @@ -1,213 +0,0 @@ -# I/O Riot NG: 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. - -``` - .---. - / \ - \.@-@./ - /`\_/`\ - // _ \\ - | \ )|_ - /`\_`> <_/ \ -jgs\__/'---'\__/ -``` - -[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 - -* [⇢ I/O Riot NG: a guided tour](#io-riot-ng-a-guided-tour) -* [⇢ ⇢ What it does](#what-it-does) -* [⇢ ⇢ A short detour: eBPF and libbpfgo](#a-short-detour-ebpf-and-libbpfgo) -* [⇢ ⇢ 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) -* [⇢ ⇢ 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) -* [⇢ ⇢ 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. - -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. - -## 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. - -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. - -## 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 -sudo ./ior -``` - -You land on the PID picker. The default selection is "All PIDs", so Enter just dumps you straight at the dashboard. - -[](./ior-guided-tour/01-launch.gif) - -The dashboard opens on the **live flamegraph**. Bars grow as new events arrive. The whole thing is keyboard-driven: `h`/`l` walk siblings at the current depth, `j`/`k` step deeper or shallower, `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. `o` cycles the stack ordering — `comm/path/tracepoint`, `path/tracepoint/comm`, etc. — and `b` toggles the metric driving bar width between event count and total bytes. - -[](./ior-guided-tour/13-tui-flamegraph.gif) - -## The seven tabs, in 30 seconds each - -The number keys jump between tabs. `tab` and `shift+tab` step. - -`2` is **Overview** — a sparkline plus the top syscalls and top paths, the at-a-glance view. - -[](./ior-guided-tour/02-overview-tab.gif) - -`3` is **Syscalls** — a sortable table. `s` sorts by the selected column, `S` reverses. - -[](./ior-guided-tour/03-syscalls-tab.gif) - -`4` is **Files**. The interesting key here is `d`: it rolls per-file rows up into their parent directory. Essential when you've got a process touching ten thousand files in `/usr/share/`. - -[](./ior-guided-tour/04-files-tab.gif) - -`5` is **Processes** — same idea, per-process / per-comm. - -[](./ior-guided-tour/05-processes-tab.gif) - -`6` is **Latency + Gaps**. Two histograms: how long each syscall took, and the idle-on-the-same-thread gap between syscalls. The dd loop in the demo workload spreads the latency distribution out so you can actually see it. - -[](./ior-guided-tour/06-latency-gaps-tab.gif) - -`7` is **Stream** — the live tail. This is where you spend most of your time when something's actually broken. - -[](./ior-guided-tour/07-stream-live.gif) - -## The Stream tab is the good one - -`space` pauses. In pause mode, `j`/`k` and arrow keys move the row/column cursor. Hitting `Enter` on a cell pushes a new filter onto a stack, narrowing what you see. Pile them up — comm, then syscall, then file — and `Esc` pops them off LIFO when you want to back out. - -[](./ior-guided-tour/08-stream-pause-filter.gif) - -`/` and `?` are regex search forward/backward. `n` and `N` walk matches. The search runs against every column in the ring buffer and wraps at the end. Search and filtering are different beasts: search highlights and jumps, filtering hides everything that doesn't match. - -[](./ior-guided-tour/09-stream-regex-search.gif) - -`e` exports the current filtered snapshot to a CSV in the working directory. `x` does the same for the paused stream view specifically (preserving your filter stack), `X` prompts for a filename, `E` opens the most recent export in `$EDITOR`. - -[](./ior-guided-tour/10-stream-csv-export.gif) - -## Filtering, more thoroughly - -The Enter-to-push trick isn't unique to Stream. It works the same on Files, Syscalls, and Processes: highlight a row, hit Enter, and the cell value becomes a filter against the entire dashboard. Three tabs of "I see one weird path / comm / syscall, drill in" with one keystroke. - -The filter status line gives you a one-glance summary of every active frame, written like: - -* `comm~bash` — substring match on a string column. This is what Enter-on-a-cell produces for `comm`, `syscall`, and `file`. -* `pid=1234` — exact equality. Used for `pid`, `tid`, `fd`, `ret`, `bytes`. -* `latency>=5ms` / `gap>=10us` — numeric comparison with a duration suffix. The full operator set is `>`, `<`, `=`, `>=`, `<=`, `!=`. - -Stack frames AND together, so pushing `comm~bash` and then `syscall~openat` shows you bash's openat calls, not bash OR openat. `Esc` (or `F`) pops the most recent frame. - -Two other knobs do related work: - -* `p`, `t`, `o` open the PID, TID, and probe-toggle dialogs. These are global filters: they reconfigure the BPF side, so kernel-level events for excluded PIDs/probes never even reach userspace. Cheaper than filtering a firehose, but it also means the filter applies to recordings (the parquet file only contains rows the kernel let through). -* The CLI mirrors of those dialogs let you bake the same scoping into a one-shot run: `-pid`, `-tid`, `-comm`, `-path`, plus `-tps <regex>` / `-tpsExclude <regex>` for picking which tracepoints to attach in the first place. - -[](./ior-guided-tour/11-pid-tid-probe.gif) - -## Recording - -Three persistence flows, each for a different job: - -* `R` from the dashboard starts streaming **Parquet** — every event row that survives your current TUI filter goes to disk continuously. `R` again stops. Footer shows the active file or the last error. - -[](./ior-guided-tour/12-parquet-recording.gif) - -* `sudo ./ior -flamegraph -name <n>` writes one aggregated `.ior.zst` artifact at shutdown. Aggregated counters, not per-event rows. Cheaper to write, ideal for ior's native flamegraph workflow and integration tests. - -* `sudo ./ior -parquet trace.parquet` is the headless firehose — every row, no TUI, no filtering. `sudo ./ior -plain` is even lighter: CSV to stdout, pipe it into anything. - -[](./ior-guided-tour/14-headless-modes.gif) - -## Querying a parquet trace with ClickHouse - -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: - -```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 -" -``` - -``` -bash read 18432 72.10 MiB -dd write 14209 1.39 GiB -fish openat 9871 0.00 B -systemd-journ… write 4112 1.62 MiB -... -``` - -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, - quantile(0.5)(latency_ns)/1000 AS p50_us, - quantile(0.99)(latency_ns)/1000 AS p99_us - FROM file('trace.parquet', Parquet) - WHERE is_error = 1 - GROUP BY syscall - ORDER BY p99_us DESC -" -``` - -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`. - -## What's still missing - -ior is pre-alpha and basically a personal tool. The headline gaps: - -* No record/replay — that was the whole point of the original I/O Riot. The new one is a tracer, not a workload simulator. I keep going back and forth on whether to put replay back in. -* No userspace symbol resolution. Stacks are at the syscall surface, not "which line of which library called read". -* No remote / cluster mode. Single host, one trace at a time. - -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. - -[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 index c4b81886..35a4fdf9 100644 --- a/gemfeed/DRAFT-unveiling-ior-ng-part-2.md +++ b/gemfeed/DRAFT-unveiling-ior-ng-part-2.md @@ -2,9 +2,9 @@ > 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). +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." +If you came here for the dashboard tour, that's Part 1. If you want to know how the data pipeline is shaped, 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) @@ -13,6 +13,7 @@ If you came here for the dashboard tour, that's Part 1. If you want to know how [](./unveiling-ior-ng/00-logo.png) +[2026-05-08 Unveiling I/O Riot NG 1.0.0 — Part 1: a guided tour](./2026-05-08-unveiling-ior-ng-part-1.md) ## Table of Contents @@ -44,11 +45,11 @@ That's the officially supported install path, and it's the right one for anyone 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 sour |