linux-kernel - Re: [PATCHv4] psi: fix possible trigger missing in the window

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Message-ID: <YgpvwTbakWSI4TWK@cmpxchg.org>
Date:   Mon, 14 Feb 2022 10:05:37 -0500
From:   Johannes Weiner <hannes@...xchg.org>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Suren Baghdasaryan <surenb@...gle.com>,
        Huangzhaoyang <huangzhaoyang@...il.com>,
        Zhaoyang Huang <zhaoyang.huang@...soc.com>,
        Ingo Molnar <mingo@...hat.com>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCHv4] psi: fix possible trigger missing in the window

On Tue, Jan 25, 2022 at 02:56:58PM +0800, Huangzhaoyang wrote:
> From: Zhaoyang Huang <zhaoyang.huang@...soc.com>
> 
> When a new threshold breaching stall happens after a psi event was
> generated and within the window duration, the new event is not
> generated because the events are rate-limited to one per window. If
> after that no new stall is recorded then the event will not be
> generated even after rate-limiting duration has passed. This is
> happening because with no new stall, window_update will not be called
> even though threshold was previously breached. To fix this, record
> threshold breaching occurrence and generate the event once window
> duration is passed.
> 
> Suggested-by: Suren Baghdasaryan <surenb@...gle.com>
> Signed-off-by: Zhaoyang Huang <zhaoyang.huang@...soc.com>

Hey Peter, would you mind taking this through the scheduler tree? It's
got my and Suren's acks. It's not a recent regression so I'm thinking
for 5.18 is fine. Thanks!