[PATCH v3 0/4] sched/psi: Allow unprivileged PSI polling

From: Domenico Cerasuolo
Date: Wed Mar 29 2023 - 03:49:30 EST


PSI offers 2 mechanisms to get information about a specific resource
pressure. One is reading from /proc/pressure/<resource>, which gives
average pressures aggregated every 2s. The other is creating a pollable
fd for a specific resource and cgroup.

The trigger creation requires CAP_SYS_RESOURCE, and gives the
possibility to pick specific time window and threshold, spawing an RT
thread to aggregate the data.

Systemd would like to provide containers the option to monitor pressure
on their own cgroup and sub-cgroups. For example, if systemd launches a
container that itself then launches services, the container should have
the ability to poll() for pressure in individual services. But neither
the container nor the services are privileged.

The series is implemented in 4 steps in order to reduce the noise of
the change.

V3:
- restored renaming patch (#2 of 4) as suggested in review
- rebased #3 and #4 on the renaming commit

V2:
- removed renaming patch (previous 2/4) and applied suggested solution
- changed update_triggers side effect removal as suggested in review
- rebased core patch on other V2 changes

Domenico Cerasuolo (4):
sched/psi: rearrange polling code in preparation
sched/psi: rename existing poll members in preparation
sched/psi: extract update_triggers side effect
sched/psi: allow unprivileged polling of N*2s period

Documentation/accounting/psi.rst | 4 +
include/linux/psi.h | 2 +-
include/linux/psi_types.h | 43 +--
kernel/cgroup/cgroup.c | 2 +-
kernel/sched/psi.c | 432 +++++++++++++++++--------------
5 files changed, 262 insertions(+), 221 deletions(-)

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2.34.1