From: Yunsheng Lin <linyunsheng@huawei.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: <dalias@libc.org>, <linux-sh@vger.kernel.org>,
<catalin.marinas@arm.com>, <dave.hansen@linux.intel.com>,
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<linux-mips@vger.kernel.org>, <ralf@linux-mips.org>,
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<akpm@linux-foundation.org>, <linuxppc-dev@lists.ozlabs.org>,
<davem@davemloft.net>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
"Rafael J. Wysocki" <rjw@rjwysocki.net>
Subject: Re: [PATCH v2 2/9] x86: numa: check the node id consistently for x86
Date: Tue, 3 Sep 2019 16:31:11 +0800 [thread overview]
Message-ID: <06eee8d0-ce56-03da-30a5-6b07e989a5e0@huawei.com> (raw)
In-Reply-To: <20190903071111.GU2369@hirez.programming.kicks-ass.net>
On 2019/9/3 15:11, Peter Zijlstra wrote:
> On Tue, Sep 03, 2019 at 02:19:04PM +0800, Yunsheng Lin wrote:
>> On 2019/9/2 20:56, Peter Zijlstra wrote:
>>> On Mon, Sep 02, 2019 at 08:25:24PM +0800, Yunsheng Lin wrote:
>>>> On 2019/9/2 15:25, Peter Zijlstra wrote:
>>>>> On Mon, Sep 02, 2019 at 01:46:51PM +0800, Yunsheng Lin wrote:
>>>>>> On 2019/9/1 0:12, Peter Zijlstra wrote:
>>>>>
>>>>>>> 1) because even it is not set, the device really does belong to a node.
>>>>>>> It is impossible a device will have magic uniform access to memory when
>>>>>>> CPUs cannot.
>>>>>>
>>>>>> So it means dev_to_node() will return either NUMA_NO_NODE or a
>>>>>> valid node id?
>>>>>
>>>>> NUMA_NO_NODE := -1, which is not a valid node number. It is also, like I
>>>>> said, not a valid device location on a NUMA system.
>>>>>
>>>>> Just because ACPI/BIOS is shit, doesn't mean the device doesn't have a
>>>>> node association. It just means we don't know and might have to guess.
>>>>
>>>> How do we guess the device's location when ACPI/BIOS does not set it?
>>>
>>> See device_add(), it looks to the device's parent and on NO_NODE, puts
>>> it there.
>>>
>>> Lacking any hints, just stick it to node0 and print a FW_BUG or
>>> something.
>>>
>>>> It seems dev_to_node() does not do anything about that and leave the
>>>> job to the caller or whatever function that get called with its return
>>>> value, such as cpumask_of_node().
>>>
>>> Well, dev_to_node() doesn't do anything; nor should it. It are the
>>> callers of set_dev_node() that should be taking care.
>>>
>>> Also note how device_add() sets the device node to the parent device's
>>> node on NUMA_NO_NODE. Arguably we should change it to complain when it
>>> finds NUMA_NO_NODE and !parent.
>>
>> Is it possible that the node id set by device_add() become invalid
>> if the node is offlined, then dev_to_node() may return a invalid
>> node id.
>
> In that case I would expect the device to go away too. Once the memory
> controller goes away, the PCI bus connected to it cannot continue to
> function.
Ok. To summarize the discussion in order to for me to understand it
correctly:
1) Make sure device_add() set to default node0 to a device if
ACPI/BIOS does not set the node id and it has not no parent device.
2) Use '(unsigned)node_id >= nr_node_ids' to fix the
CONFIG_DEBUG_PER_CPU_MAPS version of cpumask_of_node() for x86
and arm64, x86 just has a fix from you now, a patch for arm64 is
also needed.
3) Maybe fix some other the sign bug for node id checking through the
kernel using the '(unsigned)node_id >= nr_node_ids'.
Please see if I understand it correctly or miss something.
Maybe I can begin by sending a patch about item one to see if everyone
is ok with the idea?
>
>> From the comment in select_fallback_rq(), it seems that a node can
>> be offlined, not sure if node offline process has taken cared of that?
>>
>> /*
>> * If the node that the CPU is on has been offlined, cpu_to_node()
>> * will return -1. There is no CPU on the node, and we should
>> * select the CPU on the other node.
>> */
>
> Ugh, so I disagree with that notion. cpu_to_node() mapping should be
> fixed, you simply cannot change it after boot, too much stuff relies on
> it.
>
> Setting cpu_to_node to -1 on node offline is just wrong. But alas, it
> seems this is already so.
next prev parent reply other threads:[~2019-09-03 8:32 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-31 5:58 [PATCH v2 0/9] check the node id consistently across different arches Yunsheng Lin
2019-08-31 5:58 ` [PATCH v2 1/9] arm64: numa: check the node id consistently for arm64 Yunsheng Lin
2019-08-31 5:58 ` [PATCH v2 2/9] x86: numa: check the node id consistently for x86 Yunsheng Lin
2019-08-31 8:55 ` Peter Zijlstra
2019-08-31 10:09 ` Yunsheng Lin
2019-08-31 16:12 ` Peter Zijlstra
2019-09-01 4:45 ` Something about loongson_llsc_mb 陈华才
[not found] ` <2019090410032559707512@loongson.cn>
2019-09-04 9:21 ` Peter Zijlstra
2019-09-04 10:04 ` Peter Zijlstra
2019-09-04 12:57 ` Huang Pei
2019-09-02 5:46 ` [PATCH v2 2/9] x86: numa: check the node id consistently for x86 Yunsheng Lin
2019-09-02 7:25 ` Peter Zijlstra
2019-09-02 12:25 ` Yunsheng Lin
2019-09-02 12:56 ` Peter Zijlstra
2019-09-02 18:22 ` Ingo Molnar
2019-09-02 19:14 ` Peter Zijlstra
2019-09-03 6:19 ` Yunsheng Lin
2019-09-03 7:11 ` Peter Zijlstra
2019-09-03 8:31 ` Yunsheng Lin [this message]
2019-09-02 18:17 ` Ingo Molnar
2019-09-03 7:53 ` [PATCH] x86/mm: Fix cpumask_of_node() error condition Peter Zijlstra
2019-08-31 5:58 ` [PATCH v2 3/9] alpha: numa: check the node id consistently for alpha Yunsheng Lin
2019-08-31 5:58 ` [PATCH v2 4/9] powerpc: numa: check the node id consistently for powerpc Yunsheng Lin
2019-08-31 5:58 ` [PATCH v2 5/9] s390: numa: check the node id consistently for s390 Yunsheng Lin
2019-09-02 4:05 ` kbuild test robot
2019-08-31 5:58 ` [PATCH v2 6/9] sh: numa: check the node id consistently for sh Yunsheng Lin
2019-08-31 5:58 ` [PATCH v2 7/9] sparc64: numa: check the node id consistently for sparc64 Yunsheng Lin
2019-08-31 6:53 ` David Miller
2019-08-31 8:57 ` Yunsheng Lin
2019-08-31 20:02 ` David Miller
2019-09-02 6:08 ` Yunsheng Lin
2019-09-02 15:17 ` David Miller
2019-08-31 5:58 ` [PATCH v2 8/9] mips: numa: check the node id consistently for mips ip27 Yunsheng Lin
2019-08-31 5:58 ` [PATCH v2 9/9] mips: numa: check the node id consistently for mips loongson64 Yunsheng Lin
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