From: Jiang Liu <jiang.liu@linux.intel.com>
To: Andrew Morton <akpm@linux-foundation.org>,
David Rientjes <rientjes@google.com>
Cc: "Patil, Kiran" <kiran.patil@intel.com>,
Mel Gorman <mgorman@suse.de>,
Mike Galbraith <umgwanakikbuti@gmail.com>,
Peter Zijlstra <peterz@infradead.org>,
"Wysocki, Rafael J" <rafael.j.wysocki@intel.com>,
Tang Chen <tangchen@cn.fujitsu.com>, Tejun Heo <tj@kernel.org>,
"Kirsher, Jeffrey T" <jeffrey.t.kirsher@intel.com>,
"Brandeburg, Jesse" <jesse.brandeburg@intel.com>,
"Nelson, Shannon" <shannon.nelson@intel.com>,
"Wyborny, Carolyn" <carolyn.wyborny@intel.com>,
"Skidmore, Donald C" <donald.c.skidmore@intel.com>,
"Vick, Matthew" <matthew.vick@intel.com>,
"Ronciak, John" <john.ronciak@intel.com>,
"Williams, Mitch A" <mitch.a.williams@intel.com>,
"Luck, Tony" <tony.luck@intel.com>,
"netdev@vger.kernel.org" <netdev@vger.kernel.org>,
"x86@kernel.org" <x86@kernel.org>,
"linux-hotplug@vger.kernel.org" <linux-hotplug@vger.kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"linux-mm@kvack.org" <linux-mm@kvack.org>,
"intel-wired-lan@lists.osuosl.org"
<intel-wired-lan@lists.osuosl.org>
Subject: Re: [Intel-wired-lan] [Patch V3 5/9] i40e: Use numa_mem_id() to better support memoryless node
Date: Fri, 9 Oct 2015 13:52:55 +0800 [thread overview]
Message-ID: <56175637.50102@linux.intel.com> (raw)
In-Reply-To: <20151008132037.fc3887da0818e7d011cb752f@linux-foundation.org>
On 2015/10/9 4:20, Andrew Morton wrote:
> On Wed, 19 Aug 2015 17:18:15 -0700 (PDT) David Rientjes <rientjes@google.com> wrote:
>
>> On Wed, 19 Aug 2015, Patil, Kiran wrote:
>>
>>> Acked-by: Kiran Patil <kiran.patil@intel.com>
>>
>> Where's the call to preempt_disable() to prevent kernels with preemption
>> from making numa_node_id() invalid during this iteration?
>
> David asked this question twice, received no answer and now the patch
> is in the maintainer tree, destined for mainline.
>
> If I was asked this question I would respond
>
> The use of numa_mem_id() is racy and best-effort. If the unlikely
> race occurs, the memory allocation will occur on the wrong node, the
> overall result being very slightly suboptimal performance. The
> existing use of numa_node_id() suffers from the same issue.
>
> But I'm not the person proposing the patch. Please don't just ignore
> reviewer comments!
Hi Andrew,
Apologize for the slow response due to personal reasons!
And thanks for answering the question from David. To be honest,
I didn't know how to answer this question before. Actually this
question has puzzled me for a long time when dealing with memory
hot-removal. For normal cases, it only causes sub-optimal memory
allocation if schedule event happens between querying NUMA node id
and calling alloc_pages_node(). But what happens if system run into
following execution sequence?
1) node = numa_mem_id();
2) memory hot-removal event triggers
2.1) remove affected memory
2.2) reset pgdat to zero if node becomes empty after memory removal
3) alloc_pages_node(), which may access zero-ed pgdat structure.
I haven't found a mechanism to protect system from above sequence yet,
so puzzled for a long time already:(. Does stop_machine() protect
system from such a execution sequence?
Thanks!
Gerry
>
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next prev parent reply other threads:[~2015-10-09 5:53 UTC|newest]
Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-08-17 3:18 [Patch V3 0/9] Enable memoryless node support for x86 Jiang Liu
2015-08-17 3:18 ` [Patch V3 1/9] x86, NUMA, ACPI: Online node earlier when doing CPU hot-addition Jiang Liu
2015-08-17 3:18 ` [Patch V3 2/9] kernel/profile.c: Replace cpu_to_mem() with cpu_to_node() Jiang Liu
2015-08-18 0:31 ` David Rientjes
2015-08-19 7:18 ` Jiang Liu
2015-08-20 0:00 ` David Rientjes
2015-10-09 2:35 ` Jiang Liu
2015-08-17 3:19 ` [Patch V3 3/9] sgi-xp: Replace cpu_to_node() with cpu_to_mem() to support memoryless node Jiang Liu
2015-08-18 0:25 ` David Rientjes
2015-08-19 8:20 ` Jiang Liu
2015-08-20 0:02 ` David Rientjes
2015-08-20 6:36 ` Jiang Liu
2015-10-09 5:04 ` Jiang Liu
2015-08-19 11:52 ` Robin Holt
2015-08-19 12:45 ` Jiang Liu
2015-08-17 3:19 ` [Patch V3 4/9] openvswitch: " Jiang Liu
2015-08-18 0:14 ` Pravin Shelar
2015-08-17 3:19 ` [Patch V3 5/9] i40e: Use numa_mem_id() to better " Jiang Liu
2015-08-18 0:35 ` David Rientjes
2015-08-19 22:38 ` [Intel-wired-lan] " Patil, Kiran
2015-08-20 0:18 ` David Rientjes
2015-10-08 20:20 ` Andrew Morton
2015-10-09 5:52 ` Jiang Liu [this message]
2015-10-09 9:08 ` Kamezawa Hiroyuki
2015-10-09 9:25 ` Jiang Liu
2015-08-17 3:19 ` [Patch V3 6/9] i40evf: " Jiang Liu
2015-08-17 19:03 ` [Intel-wired-lan] " Patil, Kiran
2015-08-18 21:34 ` Jeff Kirsher
2015-08-17 3:19 ` [Patch V3 7/9] x86, numa: Kill useless code to improve code readability Jiang Liu
2015-08-17 3:19 ` [Patch V3 8/9] mm: Update _mem_id_[] for every possible CPU when memory configuration changes Jiang Liu
2015-08-17 3:19 ` [Patch V3 9/9] mm, x86: Enable memoryless node support to better support CPU/memory hotplug Jiang Liu
2015-08-18 6:11 ` Tang Chen
2015-08-18 6:59 ` Jiang Liu
2015-08-18 11:28 ` Tang Chen
2015-08-18 7:31 ` Ingo Molnar
2015-08-17 21:35 ` [Patch V3 0/9] Enable memoryless node support for x86 Andrew Morton
2015-08-18 10:02 ` Tang Chen
2015-08-19 8:09 ` Jiang Liu
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