Date: Mon, 21 Jul 2014 10:33:42 -0700
From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
To: Nishanth Aravamudan <nacc@linux.vnet.ibm.com>
Cc: Jiang Liu <jiang.liu@linux.intel.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Mel Gorman <mgorman@suse.de>, David Rientjes <rientjes@google.com>,
        Mike Galbraith <umgwanakikbuti@gmail.com>,
        Peter Zijlstra <peterz@infradead.org>,
        "Rafael J . Wysocki" <rafael.j.wysocki@intel.com>,
        Dipankar Sarma <dipankar@in.ibm.com>,
        Balbir Singh <bsingharora@gmail.com>,
        Thomas Gleixner <tglx@linutronix.de>, Jens Axboe <axboe@kernel.dk>,
        Frederic Weisbecker <fweisbec@gmail.com>, Jan Kara <jack@suse.cz>,
        Ingo Molnar <mingo@kernel.org>, Christoph Hellwig <hch@infradead.org>,
        "Srivatsa S. Bhat" <srivatsa.bhat@linux.vnet.ibm.com>,
        Roman Gushchin <klamm@yandex-team.ru>, Xie XiuQi <xiexiuqi@huawei.com>,
        Tony Luck <tony.luck@intel.com>, linux-mm@kvack.org,
        linux-hotplug@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [RFC Patch V1 01/30] mm, kernel: Use cpu_to_mem()/numa_mem_id()
 to support memoryless node
Message-ID: <20140721173342.GB8690@linux.vnet.ibm.com>
Reply-To: paulmck@linux.vnet.ibm.com
References: <1405064267-11678-1-git-send-email-jiang.liu@linux.intel.com>
 <1405064267-11678-2-git-send-email-jiang.liu@linux.intel.com>
 <20140711151405.GK16041@linux.vnet.ibm.com>
 <20140721171527.GA4156@linux.vnet.ibm.com>
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On Mon, Jul 21, 2014 at 10:15:27AM -0700, Nishanth Aravamudan wrote:
> Hi Paul,
> 
> On 11.07.2014 [08:14:05 -0700], Paul E. McKenney wrote:
> > On Fri, Jul 11, 2014 at 03:37:18PM +0800, Jiang Liu wrote:
> > > When CONFIG_HAVE_MEMORYLESS_NODES is enabled, cpu_to_node()/numa_node_id()
> > > may return a node without memory, and later cause system failure/panic
> > > when calling kmalloc_node() and friends with returned node id.
> > > So use cpu_to_mem()/numa_mem_id() instead to get the nearest node with
> > > memory for the/current cpu.
> > > 
> > > If CONFIG_HAVE_MEMORYLESS_NODES is disabled, cpu_to_mem()/numa_mem_id()
> > > is the same as cpu_to_node()/numa_node_id().
> > > 
> > > Signed-off-by: Jiang Liu <jiang.liu@linux.intel.com>
> > 
> > For the rcutorture piece:
> > 
> > Acked-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
> > 
> > Or if you separate the kernel/rcu/rcutorture.c portion into a separate
> > patch, I will queue it separately.
> 
> Just FYI, based upon a separate discussion with Tejun and others, it
> seems to be preferred to avoid the proliferation of cpu_to_mem
> throughout the kernel blindly. For kthread_create_on_node(), I'm going
> to try and fix the underlying issue and so you, as the caller, should
> still specify the NUMA node you are running the kthread on
> (cpu_to_node), not where you expect the memory to come from
> (cpu_to_mem).

Even better!!!  ;-)

							Thanx, Paul

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