linux-kernel - Re: [PATCH v1] rcu: Fix and improve RCU read lock checks when !CONFIG_DEBUG_LOCK

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Date:   Fri, 14 Jul 2023 10:56:15 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Gao Xiang <hsiangkao@...ux.alibaba.com>
Cc:     Joel Fernandes <joel@...lfernandes.org>, paulmck@...nel.org,
        Sandeep Dhavale <dhavale@...gle.com>,
        Frederic Weisbecker <frederic@...nel.org>,
        Neeraj Upadhyay <quic_neeraju@...cinc.com>,
        Josh Triplett <josh@...htriplett.org>,
        Boqun Feng <boqun.feng@...il.com>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        Lai Jiangshan <jiangshanlai@...il.com>,
        Zqiang <qiang.zhang1211@...il.com>,
        Matthias Brugger <matthias.bgg@...il.com>,
        AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>,
        linux-erofs@...ts.ozlabs.org, xiang@...nel.org,
        Will Shiu <Will.Shiu@...iatek.com>, kernel-team@...roid.com,
        rcu@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org
Subject: Re: [PATCH v1] rcu: Fix and improve RCU read lock checks when
 !CONFIG_DEBUG_LOCK_ALLOC

On Fri, 14 Jul 2023 21:51:16 +0800
Gao Xiang <hsiangkao@...ux.alibaba.com> wrote:

> >> we need to work on
> >> CONFIG_PREEMPT_COUNT=n (why not?), we could just always trigger a
> >> workqueue for this.
> >>  
> > 
> > So CONFIG_PREEMPT_COUNT=n users don't deserve good performance? ;-)  
> 
> I'm not sure if non-preemptible kernel users really care about
> such sensitive latencies, I don't know, my 2 cents.

CONFIG_PREEMPT_COUNT=n is for *performance* but not for *latency*. That is,
they care about the overall performance (batch processing) but not
interactive performance.

-- Steve