linux-kernel - Re: [PATCH v2 1/1] mm: only dispaly online cpus of the numa node

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Date:   Tue, 3 Oct 2017 15:56:28 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     Will Deacon <will.deacon@....com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Zhen Lei <thunder.leizhen@...wei.com>,
        Catalin Marinas <catalin.marinas@....com>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        linux-api <linux-api@...r.kernel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-mm <linux-mm@...ck.org>,
        Tianhong Ding <dingtianhong@...wei.com>,
        Hanjun Guo <guohanjun@...wei.com>,
        Libin <huawei.libin@...wei.com>,
        Kefeng Wang <wangkefeng.wang@...wei.com>
Subject: Re: [PATCH v2 1/1] mm: only dispaly online cpus of the numa node

On Tue 03-10-17 14:47:26, Will Deacon wrote:
> On Mon, Oct 02, 2017 at 02:54:46PM -0700, Andrew Morton wrote:
> > On Mon, 2 Oct 2017 11:38:07 +0100 Will Deacon <will.deacon@....com> wrote:
> > 
> > > > When I executed numactl -H(which read /sys/devices/system/node/nodeX/cpumap
> > > > and display cpumask_of_node for each node), but I got different result on
> > > > X86 and arm64. For each numa node, the former only displayed online CPUs,
> > > > and the latter displayed all possible CPUs. Unfortunately, both Linux
> > > > documentation and numactl manual have not described it clear.
> > > > 
> > > > I sent a mail to ask for help, and Michal Hocko <mhocko@...nel.org> replied
> > > > that he preferred to print online cpus because it doesn't really make much
> > > > sense to bind anything on offline nodes.
> > > > 
> > > > Signed-off-by: Zhen Lei <thunder.leizhen@...wei.com>
> > > > Acked-by: Michal Hocko <mhocko@...e.com>
> > > > ---
> > > >  drivers/base/node.c | 12 ++++++++++--
> > > >  1 file changed, 10 insertions(+), 2 deletions(-)
> > > 
> > > Which tree is this intended to go through? I'm happy to take it via arm64,
> > > but I don't want to tread on anybody's toes in linux-next and it looks like
> > > there are already queued changes to this file via Andrew's tree.
> > 
> > I grabbed it.  I suppose there's some small risk of userspace breakage
> > so I suggest it be a 4.15-rc1 thing?
> 
> To be honest, I suspect the vast majority (if not all) code that reads this
> file was developed for x86, so having the same behaviour for arm64 sounds
> like something we should do ASAP before people try to special case with
> things like #ifdef __aarch64__.
> 
> I'd rather have this in 4.14 if possible.

Agreed!

-- 
Michal Hocko
SUSE Labs