From: Peter Zijlstra <peterz@infradead•org>
To: Michal Hocko <mhocko@kernel•org>
Cc: dalias@libc•org, linux-sh@vger•kernel.org,
catalin.marinas@arm•com, dave.hansen@linux•intel.com,
heiko.carstens@de•ibm.com, jiaxun.yang@flygoat•com,
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chenhc@lemote•com, will@kernel•org, cai@lca•pw,
linux-s390@vger•kernel.org, ysato@users•sourceforge.jp,
x86@kernel•org, Yunsheng Lin <linyunsheng@huawei•com>,
rppt@linux•ibm.com, borntraeger@de•ibm.com, dledford@redhat•com,
mingo@redhat•com, jeffrey.t.kirsher@intel•com, jhogan@kernel•org,
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anshuman.khandual@arm•com, gregkh@linuxfoundation•org,
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tbogendoerfer@suse•de, paul.burton@mips•com,
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ink@jurassic•park.msu.ru, akpm@linux-foundation•org,
robin.murphy@arm•com, davem@davemloft•net
Subject: Re: [PATCH v6] numa: make node_to_cpumask_map() NUMA_NO_NODE aware
Date: Tue, 24 Sep 2019 13:23:49 +0200 [thread overview]
Message-ID: <20190924112349.GJ2332@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <20190924105622.GH23050@dhcp22.suse.cz>
On Tue, Sep 24, 2019 at 12:56:22PM +0200, Michal Hocko wrote:
> On Tue 24-09-19 11:17:14, Peter Zijlstra wrote:
> > On Tue, Sep 24, 2019 at 09:47:51AM +0200, Michal Hocko wrote:
> > > On Mon 23-09-19 22:34:10, Peter Zijlstra wrote:
> > > > On Mon, Sep 23, 2019 at 06:52:35PM +0200, Michal Hocko wrote:
> > > [...]
> > > > > I even the
> > > > > ACPI standard is considering this optional. Yunsheng Lin has referred to
> > > > > the specific part of the standard in one of the earlier discussions.
> > > > > Trying to guess the node affinity is worse than providing all CPUs IMHO.
> > > >
> > > > I'm saying the ACPI standard is wrong.
> > >
> > > Even if you were right on this the reality is that a HW is likely to
> > > follow that standard and we cannot rule out NUMA_NO_NODE being
> > > specified. As of now we would access beyond the defined array and that
> > > is clearly a bug.
> >
> > Right, because the device node is wrong, so we fix _that_!
> >
> > > Let's assume that this is really a bug for a moment. What are you going
> > > to do about that? BUG_ON? I do not really see any solution besides to either
> > > provide something sensible or BUG_ON. If you are worried about a
> > > conditional then this should be pretty easy to solve by starting the
> > > array at -1 index and associate it with the online cpu mask.
> >
> > The same thing I proposed earlier; force the device node to 0 (or any
> > other convenient random valid value) and issue a FW_BUG message to the
> > console.
>
> Why would you "fix" anything and how do you know that node 0 is the
> right choice? I have seen setups with node 0 without any memory and
> similar unexpected things.
We don't know 0 is right; but we know 'unkown' is wrong, so we FW_BUG
and pick _something_.
> To be honest I really fail to see why to object to a simple semantic
> that NUMA_NO_NODE imply all usable cpus. Could you explain that please?
Because it feels wrong. The device needs to be _somewhere_. It simply
cannot be node-less.
next prev parent reply other threads:[~2019-09-24 11:27 UTC|newest]
Thread overview: 57+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-09-17 12:48 [PATCH v6] numa: make node_to_cpumask_map() NUMA_NO_NODE aware Yunsheng Lin
2019-09-21 22:38 ` Paul Burton
2019-09-23 2:31 ` Yunsheng Lin
2019-09-23 15:15 ` Peter Zijlstra
2019-09-23 15:28 ` Michal Hocko
2019-09-23 15:48 ` Peter Zijlstra
2019-09-23 16:52 ` Michal Hocko
2019-09-23 20:34 ` Peter Zijlstra
2019-09-24 1:29 ` Yunsheng Lin
2019-09-24 9:25 ` Peter Zijlstra
2019-09-24 11:07 ` Yunsheng Lin
2019-09-24 11:28 ` Peter Zijlstra
2019-09-24 11:44 ` Yunsheng Lin
2019-09-24 11:58 ` Peter Zijlstra
2019-09-24 12:09 ` Yunsheng Lin
2019-09-24 7:47 ` Michal Hocko
2019-09-24 9:17 ` Peter Zijlstra
2019-09-24 10:56 ` Michal Hocko
2019-09-24 11:23 ` Peter Zijlstra [this message]
2019-09-24 11:54 ` Michal Hocko
2019-09-24 12:09 ` Peter Zijlstra
2019-09-24 12:25 ` Michal Hocko
2019-09-24 12:43 ` Peter Zijlstra
2019-09-24 12:59 ` Peter Zijlstra
2019-09-24 13:19 ` Michal Hocko
2019-09-25 9:14 ` Yunsheng Lin
2019-09-25 10:41 ` Peter Zijlstra
2019-10-08 8:38 ` Yunsheng Lin
2019-10-09 12:25 ` Robin Murphy
2019-10-10 6:07 ` Yunsheng Lin
2019-10-10 7:32 ` Michal Hocko
2019-10-11 3:27 ` Yunsheng Lin
2019-10-11 11:15 ` Peter Zijlstra
2019-10-12 6:17 ` Yunsheng Lin
2019-10-12 7:40 ` Greg KH
2019-10-12 9:47 ` Yunsheng Lin
2019-10-12 10:40 ` Greg KH
2019-10-12 10:47 ` Greg KH
2019-10-14 8:00 ` Yunsheng Lin
2019-10-14 9:25 ` Greg KH
2019-10-14 9:49 ` Peter Zijlstra
2019-10-14 10:04 ` Greg KH
2019-10-15 10:40 ` Yunsheng Lin
2019-10-15 16:58 ` Greg KH
2019-10-16 12:07 ` Yunsheng Lin
2019-10-28 9:20 ` Yunsheng Lin
2019-10-29 8:53 ` Michal Hocko
2019-10-30 1:58 ` Yunsheng Lin
2019-10-10 8:56 ` Peter Zijlstra
2019-09-25 10:40 ` Peter Zijlstra
2019-09-25 13:25 ` Michal Hocko
2019-09-25 16:31 ` Peter Zijlstra
2019-09-25 21:45 ` Peter Zijlstra
2019-09-26 9:05 ` Peter Zijlstra
2019-09-26 12:10 ` Peter Zijlstra
2019-09-26 11:45 ` Geert Uytterhoeven
2019-09-26 12:24 ` Peter Zijlstra
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