From: Peter Zijlstra <peterz@infradead.org>
To: Yunsheng Lin <linyunsheng@huawei.com>
Cc: dalias@libc.org, linux-sh@vger.kernel.org,
catalin.marinas@arm.com, dave.hansen@linux.intel.com,
heiko.carstens@de.ibm.com, linuxarm@huawei.com,
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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 09:11:11 +0200 [thread overview]
Message-ID: <20190903071111.GU2369@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <1f48081c-c9d6-8f3e-9559-8b0bec98f125@huawei.com>
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.
> 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.
> With the above assumption that a device is always on a valid node,
> the node id returned from dev_to_node() can be safely passed to
> cpumask_of_node() without any checking?
next prev parent reply other threads:[~2019-09-03 7:13 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 [this message]
2019-09-03 8:31 ` Yunsheng Lin
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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