[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <20080902061806.GJ18288@one.firstfloor.org>
Date: Tue, 2 Sep 2008 08:18:06 +0200
From: Andi Kleen <andi@...stfloor.org>
To: "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Cc: Andi Kleen <andi@...stfloor.org>, linux-kernel@...r.kernel.org,
cl@...ux-foundation.org, mingo@...e.hu, akpm@...ux-foundation.org,
manfred@...orfullife.com, dipankar@...ibm.com,
josht@...ux.vnet.ibm.com, schamp@....com, niv@...ibm.com,
dvhltc@...ibm.com, ego@...ibm.com, laijs@...fujitsu.com,
rostedt@...dmis.org, peterz@...radead.org
Subject: Re: [PATCH, RFC, tip/core/rcu] v3 scalable classic RCU implementation
> > It would be better if you hung rcu_irq_enter in the irq_enter() if
> > statement that checks if the task was idle or not. This way it would
> > be zero overhead for interruptions of non busy CPUs, keeping
Sorry that should have been "non idle CPUs" of course.
> > it out of many fast paths.
> >
> > Haven't read everything, sorry.
>
> So that I lose the #else above, and so that irq_enter() and irq_exit()
> look something like the following (with additional adjustments to suit)?
Yes looks good.
BTW I wonder if the compiler CSEs the idle_cpu() check properly.
> void irq_enter(void)
> {
> #ifdef CONFIG_NO_HZ
> int cpu = smp_processor_id();
> if (idle_cpu(cpu) && !in_interrupt())
> tick_nohz_stop_idle(cpu);
> #endif
> __irq_enter();
> #ifdef CONFIG_NO_HZ
> if (idle_cpu(cpu)) {
> rcu_irq_enter();
> tick_nohz_update_jiffies();
> }
> #endif
-Andi
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
Powered by blists - more mailing lists