linux-kernel - Re: [PATCH 0/2] sparc64: Use low latency path to resume idle cpu

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Message-Id: <20170721.044510.1044996118554999021.davem@davemloft.net>
Date:   Fri, 21 Jul 2017 04:45:10 +0100 (WEST)
From:   David Miller <davem@...emloft.net>
To:     vijay.ac.kumar@...cle.com
Cc:     sparclinux@...r.kernel.org, rob.gardner@...cle.com,
        anthony.yznaga@...cle.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 0/2] sparc64: Use low latency path to resume idle cpu

From: Vijay Kumar <vijay.ac.kumar@...cle.com>
Date: Thu, 20 Jul 2017 22:36:42 -0500

> I can give a try :). But looks to me one thing that will go wrong is
> irq accounting done in __irq_enter() and rcu_irq_enter().

Actually, the bigger problem is that scheduler_ipi() can raise a
software interrupt, and nothing will invoke it.

It's turning quite ugly to avoid the IRQ overhead, I must admit.
So ignore this for now.

In the longer term a probably cleaner way to do this is to have
a special direct version of scheduler_ipi() that invokes all the
necessary work, even the rebalance softirq, directly rather than
indirectly.