PERF-IOSTAT(1)

📦
version 7.3.1 · 39 versions
, in arch rolling

💅 PERF-IOSTAT(1) — the perf iostat glow-up 🎀

okay bestie, so this is perf iostat, and it lives in the perf manual (yes, that perf ✨), and honestly? it's giving "I want to know exactly how much data my PCIe root ports are slinging around" and ngl it ate. 🔥

✨ NAME ✨

perf-iostat — show I/O performance metrics 🦋

🌸 SYNOPSIS 🌸

perf iostat list
perf iostat <ports> -- <command> [<options>]

💖 DESCRIPTION 💖

so this mode is literally designed to hand you four I/O performance metrics per each PCIe root port. four. metrics. per port. periodt. 💅

  • Inbound Read — I/O devices below the root port read from the host memory, in MB
  • Inbound Write — I/O devices below the root port write to the host memory, in MB
  • Outbound Read — CPU reads from I/O devices below the root port, in MB
  • Outbound Write — CPU writes to I/O devices below the root port, in MB

like, that's the whole vibe check: who's reading, who's writing, and which direction the bytes are going. 🫶

🌈 OPTIONS 🌈

  • <command>... — literally any command you can specify in a shell, bestie. go wild. 🧚
  • list — list all the PCIe root ports. all of them. 👑
  • <ports> — select which root ports you want to monitor. a comma-separated list is supported, so you can pick a lil squad instead of the whole group chat. 💜

⭐ EXAMPLES ⭐

1. list all PCIe root ports (example for 2-S platform) 🎀

$ perf iostat list
S0-uncore_iio_0<0000:00>
S1-uncore_iio_0<0000:80>
S0-uncore_iio_1<0000:17>
S1-uncore_iio_1<0000:85>
S0-uncore_iio_2<0000:3a>
S1-uncore_iio_2<0000:ae>
S0-uncore_iio_3<0000:5d>
S1-uncore_iio_3<0000:d7>

look at them all lined up. iconic behavior honestly. ✨

2. collect metrics for all PCIe root ports 🔥

$ perf iostat -- dd if=/dev/zero of=/dev/nvme0n1 bs=1M oflag=direct
357708+0 records in
357707+0 records out
375083606016 bytes (375 GB, 349 GiB) copied, 215.974 s, 1.7 GB/s

Performance counter stats for 'system wide':

   port             Inbound Read(MB)    Inbound Write(MB)    Outbound Read(MB)   Outbound Write(MB)
0000:00                    1                    0                    2                    3
0000:80                    0                    0                    0                    0
0000:17               352552                   43                    0                   21
0000:85                    0                    0                    0                    0
0000:3a                    3                    0                    0                    0
0000:ae                    0                    0                    0                    0
0000:5d                    0                    0                    0                    0
0000:d7                    0                    0                    0                    0

not the 0000:17 port absolutely carrying the entire team with 352552 inbound read MB 😭 main character energy fr fr.

3. collect metrics for a comma-separated list of PCIe root ports 💫

$ perf iostat 0000:17,0:3a -- dd if=/dev/zero of=/dev/nvme0n1 bs=1M oflag=direct
357708+0 records in
357707+0 records out
375083606016 bytes (375 GB, 349 GiB) copied, 197.08 s, 1.9 GB/s

Performance counter stats for 'system wide':

   port             Inbound Read(MB)    Inbound Write(MB)    Outbound Read(MB)   Outbound Write(MB)
0000:17               358559                   44                    0                   22
0000:3a                    3                    2                    0                    0

197.081983474 seconds time elapsed

see how we only invited two ports to the party? that's the comma-separated list doing its thing. so slay. 💅

🦋 SEE ALSO 🦋

lowkey reminder: keep <ports> comma-separated and don't forget the -- before your <command> and [<options>], bestie. the vibes depend on it. 🙈

✨ that's the whole page! ✨ this gem is from the perf manual, dated 10/31/2026 — written by perf, and it's PERF-IOSTAT(1) all day every day. go collect some metrics, you absolute legend 💜🎀🌸

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