From: Peter Zijlstra <peterz@infradead.org>
To: Lai Jiangshan <laijs@cn.fujitsu.com>
Cc: Oleg Nesterov <oleg@redhat.com>,
Gautham R Shenoy <ego@in.ibm.com>,
Rusty Russell <rusty@rustcorp.com.au>,
Benjamin Herrenschmidt <benh@kernel.crashing.org>,
Hugh Dickins <hugh.dickins@tiscali.co.uk>,
Ingo Molnar <mingo@elte.hu>,
"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
Nathan Fontenot <nfont@austin.ibm.com>,
Andrew Morton <akpm@linux-foundation.org>,
Thomas Gleixner <tglx@linutronix.de>,
Sachin Sant <sachinp@in.ibm.com>,
"H. Peter Anvin" <hpa@zytor.com>,
Shane Wang <shane.wang@intel.com>,
Roland McGrath <roland@redhat.com>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH 2/2] cpuhotplug: make get_online_cpus() scalability by using percpu counter
Date: Mon, 12 Apr 2010 11:28:59 +0200 [thread overview]
Message-ID: <1271064539.4222.27.camel@twins> (raw)
In-Reply-To: <4BC2E6CE.7060401@cn.fujitsu.com>
On Mon, 2010-04-12 at 17:24 +0800, Lai Jiangshan wrote:
> Oleg Nesterov wrote:
> > On 04/07, Oleg Nesterov wrote:
> >> On 04/07, Lai Jiangshan wrote:
> >>> Old get_online_cpus() is read-preference, I think the goal of this ability
> >>> is allow get_online_cpus()/put_online_cpus() to be called nested.
> >> Sure, I understand why you added task_struct->get_online_cpus_nest.
> >>
> >>> and use per-task counter for allowing get_online_cpus()/put_online_cpus()
> >>> to be called nested, I think this deal is absolutely worth.
> >> As I said, I am not going to argue. I can't justify this tradeoff.
> >
> > But, I must admit, I'd like to avoid adding the new member to task_struct.
> >
> > What do you think about the code below?
> >
> > I didn't even try to compile it, just to explain what I mean.
> >
> > In short: we have the per-cpu fast counters, plus the slow counter
> > which is only used when cpu_hotplug_begin() is in progress.
> >
> > Oleg.
> >
>
> get_online_cpus() in your code is still read-preference.
> I wish we quit this ability of get_online_cpus().
Why?
next prev parent reply other threads:[~2010-04-12 9:32 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-04-05 10:38 [PATCH 2/2] cpuhotplug: make get_online_cpus() scalability by using percpu counter Lai Jiangshan
2010-04-05 16:29 ` Oleg Nesterov
2010-04-06 12:00 ` Oleg Nesterov
2010-04-07 13:35 ` Lai Jiangshan
2010-04-07 13:54 ` Oleg Nesterov
2010-04-09 12:12 ` Oleg Nesterov
2010-04-12 9:24 ` Lai Jiangshan
2010-04-12 9:28 ` Peter Zijlstra [this message]
2010-04-12 12:30 ` Lai Jiangshan
2010-04-12 12:34 ` Peter Zijlstra
2010-04-13 1:47 ` Lai Jiangshan
2010-04-12 18:16 ` Oleg Nesterov
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