linux-kernel - Re: [PATCH 0/2] measure latency of cpu hotplug path

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Message-ID: <20200924083414.GB1362448@hirez.programming.kicks-ass.net>
Date:   Thu, 24 Sep 2020 10:34:14 +0200
From:   peterz@...radead.org
To:     Prasad Sodagudi <psodagud@...eaurora.org>
Cc:     rostedt@...dmis.org, tglx@...utronix.de, qais.yousef@....com,
        mingo@...nel.org, cai@....pw, tyhicks@...onical.com, arnd@...db.de,
        rameezmustafa@...eaurora.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 0/2] measure latency of cpu hotplug path

On Wed, Sep 23, 2020 at 04:37:44PM -0700, Prasad Sodagudi wrote:
> There are all changes related to cpu hotplug path and would like to seek
> upstream review. These are all patches in Qualcomm downstream kernel
> for a quite long time. First patch sets the rt prioity to hotplug
> task and second patch adds cpuhp trace events.
> 
> 1) cpu-hotplug: Always use real time scheduling when hotplugging a CPU
> 2) cpu/hotplug: Add cpuhp_latency trace event

Why? Hotplug is a known super slow path. If you care about hotplug
latency you're doing it wrong.