linux-kernel - Re: [PATCH 0/4] sched/psi: Allow unprivileged PSI polling

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Message-ID: <CAJuCfpGYrnCoAn+bUdcEZ3OS+5ujDp2iUNXBMRacxNGbJvCY-w@mail.gmail.com>
Date:   Mon, 13 Mar 2023 08:29:37 -0700
From:   Suren Baghdasaryan <surenb@...gle.com>
To:     Domenico Cerasuolo <cerasuolodomenico@...il.com>
Cc:     linux-kernel@...r.kernel.org, peterz@...radead.org,
        brauner@...nel.org, chris@...isdown.name, hannes@...xchg.org
Subject: Re: [PATCH 0/4] sched/psi: Allow unprivileged PSI polling

On Thu, Mar 9, 2023 at 9:08 AM Domenico Cerasuolo
<cerasuolodomenico@...il.com> wrote:
>
> 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.

This sounds like an interesting usecase. I'll need to take a closer
look once I'm back from vacation later this week.
Thanks!

>
> The series is implemented in 4 steps in order to reduce the noise of
> the change.
>
> 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               | 412 ++++++++++++++++---------------
>  5 files changed, 250 insertions(+), 213 deletions(-)
>
> --
> 2.34.1
>