linux-kernel - Re: [RFC Patch V1 01/30] mm, kernel: Use cpu_to_mem()/numa_mem

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Message-ID: <20140721171527.GA4156@linux.vnet.ibm.com>
Date:	Mon, 21 Jul 2014 10:15:27 -0700
From:	Nishanth Aravamudan <nacc@...ux.vnet.ibm.com>
To:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Cc:	Jiang Liu <jiang.liu@...ux.intel.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Mel Gorman <mgorman@...e.de>,
	David Rientjes <rientjes@...gle.com>,
	Mike Galbraith <umgwanakikbuti@...il.com>,
	Peter Zijlstra <peterz@...radead.org>,
	"Rafael J . Wysocki" <rafael.j.wysocki@...el.com>,
	Dipankar Sarma <dipankar@...ibm.com>,
	Balbir Singh <bsingharora@...il.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Jens Axboe <axboe@...nel.dk>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Jan Kara <jack@...e.cz>, Ingo Molnar <mingo@...nel.org>,
	Christoph Hellwig <hch@...radead.org>,
	"Srivatsa S. Bhat" <srivatsa.bhat@...ux.vnet.ibm.com>,
	Roman Gushchin <klamm@...dex-team.ru>,
	Xie XiuQi <xiexiuqi@...wei.com>,
	Tony Luck <tony.luck@...el.com>, linux-mm@...ck.org,
	linux-hotplug@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC Patch V1 01/30] mm, kernel: Use cpu_to_mem()/numa_mem_id()
 to support memoryless node

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@...ux.intel.com>
> 
> For the rcutorture piece:
> 
> Acked-by: Paul E. McKenney <paulmck@...ux.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).

Thanks,
Nish

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