linux-kernel - Re: [PATCH v3] rcu/nocb: Avoid polling when myrdp->nocb_head

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Date:   Tue, 14 Jun 2022 13:42:19 +0200
From:   Frederic Weisbecker <frederic@...nel.org>
To:     Zqiang <qiang1.zhang@...el.com>
Cc:     paulmck@...nel.org, rcu@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3] rcu/nocb: Avoid polling when myrdp->nocb_head_rdp
 list is empty

On Sat, Jun 11, 2022 at 07:00:44PM +0800, Zqiang wrote:
> Currently, If the 'rcu_nocb_poll' bootargs is enable, all rcuog kthreads
> enter polling mode. however, due to only insert CPU's rdp which belong to
> rcu_nocb_mask to 'nocb_head_rdp' list or all CPU's rdp served by rcuog
> kthread have been de-offloaded, these cause the 'nocb_head_rdp' list
> served by rcuog kthread is empty, when the 'nocb_head_rdp' is empty,
> the rcuog kthread in polling mode not actually do anything. fix it by
> exiting polling mode when the 'nocb_head_rdp'list is empty, otherwise
> entering polling mode.
> 
> Co-developed-by: Frederic Weisbecker <frederic@...nel.org>

Acked-by: Frederic Weisbecker <frederic@...nel.org>

Thanks!

(might be worth testing with TREE01 and --bootargs "rcu_gp_poll" )