linux-kernel - [PATCH] psi: reduce min window size to 50ms

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Date:   Fri, 10 Feb 2023 14:31:01 -0800
From:   Sudarshan Rajagopalan <quic_sudaraja@...cinc.com>
To:     David Hildenbrand <david@...hat.com>,
        Johannes Weiner <hannes@...xchg.org>,
        Suren Baghdasaryan <surenb@...gle.com>,
        Mike Rapoport <rppt@...nel.org>,
        Oscar Salvador <osalvador@...e.de>,
        Anshuman Khandual <anshuman.khandual@....com>,
        mark.rutland@....com, will@...nel.org,
        virtualization@...ts.linux-foundation.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-arm-msm@...r.kernel.org
Cc:     Sudarshan Rajagopalan <quic_sudaraja@...cinc.com>,
        Trilok Soni <quic_tsoni@...cinc.com>,
        Sukadev Bhattiprolu <quic_sukadev@...cinc.com>,
        Srivatsa Vaddagiri <quic_svaddagi@...cinc.com>,
        Patrick Daly <quic_pdaly@...cinc.com>
Subject: [PATCH] psi: reduce min window size to 50ms

The PSI mechanism is useful tool to monitor pressure stall
information in the system. Currently, the minimum window size
is set to 500ms. May we know what is the rationale for this?

For lightweight systems such as Linux Embedded Systems, PSI
can be used to monitor and track memory pressure building up
in the system and respond quickly to such memory demands.
Example, the Linux Embedded Systems could be a secondary VM
system which requests for memory from Primary host. With 500ms
window size, the sampling period is 50ms (one-tenth of windwo
size). So the minimum amount of time the process needs to stall,
so that a PSI event can be generated and actions can be done
is 50ms. This reaction time can be much reduced by reducing the
sampling time (by reducing window size), so that responses to
such memory pressures in system can be serviced much quicker.

Please let us know your thoughts on reducing window size to 50ms.

Sudarshan Rajagopalan (1):
  psi: reduce min window size to 50ms

 kernel/sched/psi.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

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2.7.4