[PATCH] docs: accounting/psi: drop stale 500ms window minimum from trigger docs

[PATCH] docs: accounting/psi: drop stale 500ms window minimum from trigger docs

[Tao Cui]

From: Tao Cui <cuitao@kylinos.cn>

psi.rst says trigger windows range "from 500ms to 10s" with a 50ms min
polling interval. That minimum was removed in commit 519fabc7aaba ("psi:
remove 500ms min window size limitation for triggers"): the polling-rate
protection moved to gating trigger creation behind CAP_SYS_RESOURCE,
which also stopped capping psi event latency.

Update the wording accordingly: windows up to 10s with no enforced
minimum; trigger creation requires CAP_SYS_RESOURCE on cgroup pressure
files, while unprivileged users on /proc/pressure/ are limited to 2s
multiples.

Signed-off-by: Tao Cui <cuitao@kylinos.cn>
---
 Documentation/accounting/psi.rst | 17 ++++++++---------
 1 file changed, 8 insertions(+), 9 deletions(-)

diff --git a/Documentation/accounting/psi.rst b/Documentation/accounting/psi.rst
index d455db3e5808..aae57fb5f15c 100644
--- a/Documentation/accounting/psi.rst
+++ b/Documentation/accounting/psi.rst
@@ -99,15 +99,14 @@ psi metric and deactivates upon exit from the stall state. While system is
 in the stall state psi signal growth is monitored at a rate of 10 times per
 tracking window.
 
-The kernel accepts window sizes ranging from 500ms to 10s, therefore min
-monitoring update interval is 50ms and max is 1s. Min limit is set to
-prevent overly frequent polling. Max limit is chosen as a high enough number
-after which monitors are most likely not needed and psi averages can be used
-instead.
-
-Unprivileged users can also create monitors, with the only limitation that the
-window size must be a multiple of 2s, in order to prevent excessive resource
-usage.
+The kernel accepts window sizes up to 10s. The 10s maximum is chosen as a
+high enough number after which monitors are most likely not needed and psi
+averages can be used instead.
+
+To prevent excessive resource usage, trigger creation is restricted to
+privileged users (CAP_SYS_RESOURCE) on cgroup pressure files; on the
+system-wide /proc/pressure/ files unprivileged users can create monitors
+as well, limited to window sizes that are a multiple of 2s.
 
 When activated, psi monitor stays active for at least the duration of one
 tracking window to avoid repeated activations/deactivations when system is
-- 
2.43.0