{
  "slug": "pressure-stall-information",
  "term": "Pressure Stall Information (PSI)",
  "aliases": [
    "PSI",
    "I/O pressure",
    "io.pressure"
  ],
  "definition": "Pressure Stall Information measures time during which tasks are stalled on CPU, memory or I/O resources.",
  "note": "For I/O pressure, some tracks intervals with at least one stalled task; full tracks intervals when all non-idle tasks are stalled simultaneously. Each line's total accumulates stall time in microseconds; avg10, avg60 and avg300 report percentage trends over their respective windows. [psi]\n\n/proc/pressure/io describes system scope; cgroup v2 io.pressure describes a group. full is a subset of some, so their totals must not be added. Neither is a device-busy percentage, request-latency percentile or sum of individual request latencies. [psi]",
  "limitations": [
    {
      "text": "System-level CPU full is undefined and reported as zero in the documented interface.",
      "citationIds": [
        "psi"
      ]
    }
  ],
  "related": [
    "cgroup-v2-io-controller",
    "process-io-accounting"
  ],
  "citations": [
    {
      "id": "psi",
      "title": "Linux 6.12: Pressure Stall Information and cgroup2 interface",
      "url": "https://docs.kernel.org/6.12/accounting/psi.html",
      "accessed": "2026-11-03"
    }
  ],
  "status": "shipping",
  "advantages": [],
  "supersedes": [],
  "supersededBy": [],
  "firstSeen": null,
  "lastSeen": null,
  "updated": "2026-11-03",
  "provenance": [
    "Source synthesis from Linux 6.12 documentation; no new host measurements or universal performance guarantee."
  ]
}