[PATCH v2 0/1] mm: only dispaly online cpus of the numa node

[PATCH v2 0/1] mm: only dispaly online cpus of the numa node

[Zhen Lei]

v1 -> v2:
Replace local variable "cpumask_var_t mask" with dynamic memory alloc: alloc_cpumask_var,
to avoid possible stack overflow.

Zhen Lei (1):
  mm: only dispaly online cpus of the numa node

 drivers/base/node.c | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

-- 
2.5.0


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

[Zhen Lei]

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@kernel.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@huawei.com>
Acked-by: Michal Hocko <mhocko@suse.com>
---
 drivers/base/node.c | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/drivers/base/node.c b/drivers/base/node.c
index 3855902..aae2402 100644
--- a/drivers/base/node.c
+++ b/drivers/base/node.c
@@ -27,13 +27,21 @@ static struct bus_type node_subsys = {
 
 static ssize_t node_read_cpumap(struct device *dev, bool list, char *buf)
 {
+	ssize_t n;
+	cpumask_var_t mask;
 	struct node *node_dev = to_node(dev);
-	const struct cpumask *mask = cpumask_of_node(node_dev->dev.id);
 
 	/* 2008/04/07: buf currently PAGE_SIZE, need 9 chars per 32 bits. */
 	BUILD_BUG_ON((NR_CPUS/32 * 9) > (PAGE_SIZE-1));
 
-	return cpumap_print_to_pagebuf(list, buf, mask);
+	if (!alloc_cpumask_var(&mask, GFP_KERNEL))
+		return 0;
+
+	cpumask_and(mask, cpumask_of_node(node_dev->dev.id), cpu_online_mask);
+	n = cpumap_print_to_pagebuf(list, buf, mask);
+	free_cpumask_var(mask);
+
+	return n;
 }
 
 static inline ssize_t node_read_cpumask(struct device *dev,
-- 
2.5.0


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

[Will Deacon]

[+akpm]

Hi Thunder,

On Fri, Sep 29, 2017 at 05:53:25PM +0800, Zhen Lei 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@kernel.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@huawei.com>
> Acked-by: Michal Hocko <mhocko@suse.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.

Will

> diff --git a/drivers/base/node.c b/drivers/base/node.c
> index 3855902..aae2402 100644
> --- a/drivers/base/node.c
> +++ b/drivers/base/node.c
> @@ -27,13 +27,21 @@ static struct bus_type node_subsys = {
>  
>  static ssize_t node_read_cpumap(struct device *dev, bool list, char *buf)
>  {
> +	ssize_t n;
> +	cpumask_var_t mask;
>  	struct node *node_dev = to_node(dev);
> -	const struct cpumask *mask = cpumask_of_node(node_dev->dev.id);
>  
>  	/* 2008/04/07: buf currently PAGE_SIZE, need 9 chars per 32 bits. */
>  	BUILD_BUG_ON((NR_CPUS/32 * 9) > (PAGE_SIZE-1));
>  
> -	return cpumap_print_to_pagebuf(list, buf, mask);
> +	if (!alloc_cpumask_var(&mask, GFP_KERNEL))
> +		return 0;
> +
> +	cpumask_and(mask, cpumask_of_node(node_dev->dev.id), cpu_online_mask);
> +	n = cpumap_print_to_pagebuf(list, buf, mask);
> +	free_cpumask_var(mask);
> +
> +	return n;
>  }
>  
>  static inline ssize_t node_read_cpumask(struct device *dev,
> -- 
> 2.5.0
> 
> 

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

[Andrew Morton]

On Mon, 2 Oct 2017 11:38:07 +0100 Will Deacon <will.deacon@arm.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@kernel.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@huawei.com>
> > Acked-by: Michal Hocko <mhocko@suse.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?

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

[Will Deacon]

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@arm.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@kernel.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@huawei.com>
> > > Acked-by: Michal Hocko <mhocko@suse.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.

Cheers,

Will

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

[Michal Hocko]

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@arm.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@kernel.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@huawei.com>
> > > > Acked-by: Michal Hocko <mhocko@suse.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

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

[Leizhen (ThunderTown)]

On 2017/10/3 21:56, Michal Hocko wrote:
> 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@arm.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@kernel.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@huawei.com>
>>>>> Acked-by: Michal Hocko <mhocko@suse.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!
> 

+1

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Thanks!
BestRegards

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

[Michael Ellerman]

Zhen Lei <thunder.leizhen@huawei.com> writes:

> 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.

FWIW powerpc happens to implement the x86 behaviour, online CPUs only.

cheers

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