[RFC PATCH V4 0/1] mm: add last level page table numa info to /proc/pid/numa_pgtable

[RFC PATCH V4 0/1] mm: add last level page table numa info to /proc/pid/numa_pgtable

[Xin Hao]

In many data center servers, the shared memory architectures is
Non-Uniform Memory Access (NUMA), remote numa node data access
often brings a high latency problem, but what we are easy to ignore
is that the page table remote numa access, It can also leads to a
performance degradation.

So there add a new interface in /proc, This will help developers to
get more info about performance issues if they are caused by cross-NUMA.

V4 -> V3
1, Add some detects and spinlock when operating PMD page as Baolin Wang advised.

V2 -> V3
1, Fix compile warning bug.

V1 -> V2
1, As Matthew Wilcox advise, Simplify the code.
2, Do some codes format fix.

V3: https://lore.kernel.org/linux-mm/20220801032704.64356-1-xhao@linux.alibaba.com/
V2: https://lore.kernel.org/linux-mm/20220731155223.60238-1-xhao@linux.alibaba.com/
V1: https://lore.kernel.org/linux-mm/YuVqdcY8Ibib2LJa@casper.infradead.org/T/


Xin Hao (1):
  mm: add last level page table numa info to /proc/pid/numa_pgtable

 fs/proc/base.c     |  2 ++
 fs/proc/internal.h |  1 +
 fs/proc/task_mmu.c | 87 ++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 90 insertions(+)

--
2.31.0

[RFC PATCH V4 1/1] mm: add last level page table numa info to /proc/pid/numa_pgtable

[Xin Hao]

In many data center servers, the shared memory architectures is
Non-Uniform Memory Access (NUMA), remote numa node data access
often brings a high latency problem, but what we are easy to ignore
is that the page table remote numa access, It can also leads to a
performance degradation.

So there add a new interface in /proc, This will help developers to
get more info about performance issues if they are caused by cross-NUMA.

Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Xin Hao <xhao@linux.alibaba.com>
---
 fs/proc/base.c     |  2 ++
 fs/proc/internal.h |  1 +
 fs/proc/task_mmu.c | 87 ++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 90 insertions(+)

diff --git a/fs/proc/base.c b/fs/proc/base.c
index 8dfa36a99c74..487e82dd3275 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -3224,6 +3224,7 @@ static const struct pid_entry tgid_base_stuff[] = {
 	REG("maps",       S_IRUGO, proc_pid_maps_operations),
 #ifdef CONFIG_NUMA
 	REG("numa_maps",  S_IRUGO, proc_pid_numa_maps_operations),
+	REG("numa_pgtable", S_IRUGO, proc_pid_numa_pgtable_operations),
 #endif
 	REG("mem",        S_IRUSR|S_IWUSR, proc_mem_operations),
 	LNK("cwd",        proc_cwd_link),
@@ -3571,6 +3572,7 @@ static const struct pid_entry tid_base_stuff[] = {
 #endif
 #ifdef CONFIG_NUMA
 	REG("numa_maps", S_IRUGO, proc_pid_numa_maps_operations),
+	REG("numa_pgtable", S_IRUGO, proc_pid_numa_pgtable_operations),
 #endif
 	REG("mem",       S_IRUSR|S_IWUSR, proc_mem_operations),
 	LNK("cwd",       proc_cwd_link),
diff --git a/fs/proc/internal.h b/fs/proc/internal.h
index 06a80f78433d..e7ed9ef097b6 100644
--- a/fs/proc/internal.h
+++ b/fs/proc/internal.h
@@ -296,6 +296,7 @@ struct mm_struct *proc_mem_open(struct inode *inode, unsigned int mode);

 extern const struct file_operations proc_pid_maps_operations;
 extern const struct file_operations proc_pid_numa_maps_operations;
+extern const struct file_operations proc_pid_numa_pgtable_operations;
 extern const struct file_operations proc_pid_smaps_operations;
 extern const struct file_operations proc_pid_smaps_rollup_operations;
 extern const struct file_operations proc_clear_refs_operations;
diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index 2d04e3470d4c..77b7a49757f5 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -1999,4 +1999,91 @@ const struct file_operations proc_pid_numa_maps_operations = {
 	.release	= proc_map_release,
 };

+struct pgtable_numa_private {
+	struct proc_maps_private proc_maps;
+	unsigned long node[MAX_NUMNODES];
+};
+
+static int gather_pgtable_numa_stats(pmd_t *pmd, unsigned long addr,
+				     unsigned long end, struct mm_walk *walk)
+{
+	struct pgtable_numa_private *priv = walk->private;
+	struct page *page;
+	int nid;
+
+	if (pmd_huge(*pmd)) {
+		page = virt_to_page(pmd);
+	} else {
+		page = pmd_page(*pmd);
+	}
+
+	nid = page_to_nid(page);
+	priv->node[nid]++;
+
+	return 0;
+}
+
+static const struct mm_walk_ops show_numa_pgtable_ops = {
+	.pmd_entry = gather_pgtable_numa_stats,
+};
+
+/*
+ * Display the page talbe allocated per node via /proc.
+ */
+static int show_numa_pgtable(struct seq_file *m, void *v)
+{
+	struct pgtable_numa_private *numa_priv = m->private;
+	struct vm_area_struct *vma = v;
+	struct mm_struct *mm = vma->vm_mm;
+	struct file *file = vma->vm_file;
+	int nid;
+
+	if (!mm)
+		return 0;
+
+	memset(numa_priv->node, 0, sizeof(numa_priv->node));
+
+	seq_printf(m, "%08lx ", vma->vm_start);
+
+	if (file) {
+		seq_puts(m, " file=");
+		seq_file_path(m, file, "\n\t= ");
+	} else if (vma->vm_start <= mm->brk && vma->vm_end >= mm->start_brk) {
+		seq_puts(m, " heap");
+	} else if (is_stack(vma)) {
+		seq_puts(m, " stack");
+	}
+
+	/* mmap_lock is held by m_start */
+	walk_page_vma(vma, &show_numa_pgtable_ops, numa_priv);
+
+	for_each_node_state(nid, N_MEMORY) {
+		if (numa_priv->node[nid])
+			seq_printf(m, " N%d=%lu", nid, numa_priv->node[nid]);
+	}
+	seq_putc(m, '\n');
+
+	return 0;
+}
+
+static const struct seq_operations proc_pid_numa_pgtable_op = {
+	.start  = m_start,
+	.next   = m_next,
+	.stop   = m_stop,
+	.show   = show_numa_pgtable,
+};
+
+static int pid_numa_pgtable_open(struct inode *inode, struct file *file)
+{
+	return proc_maps_open(inode, file, &proc_pid_numa_pgtable_op,
+			sizeof(struct pgtable_numa_private));
+}
+
+const struct file_operations proc_pid_numa_pgtable_operations = {
+	.open		= pid_numa_pgtable_open,
+	.read		= seq_read,
+	.llseek		= seq_lseek,
+	.release	= proc_map_release,
+};
+
 #endif /* CONFIG_NUMA */
--
2.31.0

Re: [RFC PATCH V4 1/1] mm: add last level page table numa info to /proc/pid/numa_pgtable

[David Hildenbrand]

On 01.08.22 14:17, Xin Hao wrote:
> In many data center servers, the shared memory architectures is
> Non-Uniform Memory Access (NUMA), remote numa node data access
> often brings a high latency problem, but what we are easy to ignore
> is that the page table remote numa access, It can also leads to a
> performance degradation.

Let me try rewriting:

"
Many data center servers employ Non-Uniform Memory Access (NUMA)
architectures. Remote numa memory access results in high latency. While
memory placement is one issue, sub-optimal page table placement can also
result in surprise performance degradation.
"

> 
> So there add a new interface in /proc, This will help developers to
> get more info about performance issues if they are caused by cross-NUMA.


Why do we only care about "last level page table", why not about the others?

IMHO, we could emit something like "0, 1, 3, 0" instead for a given user
space address, showing the NUMA node the page table belongs to from
highest to lowest page table level.

> 
> Reported-by: kernel test robot <lkp@intel.com>

The kernel test robot reported that we need "/proc/pid/numa_pgtable" ?! :)

Just drop that unless it's a follow-up fix.

> Signed-off-by: Xin Hao <xhao@linux.alibaba.com>
> ---
>  fs/proc/base.c     |  2 ++
>  fs/proc/internal.h |  1 +
>  fs/proc/task_mmu.c | 87 ++++++++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 90 insertions(+)
> 
> diff --git a/fs/proc/base.c b/fs/proc/base.c
> index 8dfa36a99c74..487e82dd3275 100644
> --- a/fs/proc/base.c
> +++ b/fs/proc/base.c
> @@ -3224,6 +3224,7 @@ static const struct pid_entry tgid_base_stuff[] = {
>  	REG("maps",       S_IRUGO, proc_pid_maps_operations),
>  #ifdef CONFIG_NUMA
>  	REG("numa_maps",  S_IRUGO, proc_pid_numa_maps_operations),
> +	REG("numa_pgtable", S_IRUGO, proc_pid_numa_pgtable_operations),
>  #endif
>  	REG("mem",        S_IRUSR|S_IWUSR, proc_mem_operations),
>  	LNK("cwd",        proc_cwd_link),
> @@ -3571,6 +3572,7 @@ static const struct pid_entry tid_base_stuff[] = {
>  #endif
>  #ifdef CONFIG_NUMA
>  	REG("numa_maps", S_IRUGO, proc_pid_numa_maps_operations),
> +	REG("numa_pgtable", S_IRUGO, proc_pid_numa_pgtable_operations),
>  #endif
>  	REG("mem",       S_IRUSR|S_IWUSR, proc_mem_operations),
>  	LNK("cwd",       proc_cwd_link),
> diff --git a/fs/proc/internal.h b/fs/proc/internal.h
> index 06a80f78433d..e7ed9ef097b6 100644
> --- a/fs/proc/internal.h
> +++ b/fs/proc/internal.h
> @@ -296,6 +296,7 @@ struct mm_struct *proc_mem_open(struct inode *inode, unsigned int mode);
> 
>  extern const struct file_operations proc_pid_maps_operations;
>  extern const struct file_operations proc_pid_numa_maps_operations;
> +extern const struct file_operations proc_pid_numa_pgtable_operations;
>  extern const struct file_operations proc_pid_smaps_operations;
>  extern const struct file_operations proc_pid_smaps_rollup_operations;
>  extern const struct file_operations proc_clear_refs_operations;
> diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
> index 2d04e3470d4c..77b7a49757f5 100644
> --- a/fs/proc/task_mmu.c
> +++ b/fs/proc/task_mmu.c
> @@ -1999,4 +1999,91 @@ const struct file_operations proc_pid_numa_maps_operations = {
>  	.release	= proc_map_release,
>  };
> 
> +struct pgtable_numa_private {
> +	struct proc_maps_private proc_maps;
> +	unsigned long node[MAX_NUMNODES];
> +};
> +
> +static int gather_pgtable_numa_stats(pmd_t *pmd, unsigned long addr,
> +				     unsigned long end, struct mm_walk *walk)
> +{
> +	struct pgtable_numa_private *priv = walk->private;
> +	struct page *page;
> +	int nid;
> +
> +	if (pmd_huge(*pmd)) {
> +		page = virt_to_page(pmd);
> +	} else {
> +		page = pmd_page(*pmd);
> +	}
> +
> +	nid = page_to_nid(page);
> +	priv->node[nid]++;
> +
> +	return 0;
> +}
> +
> +static const struct mm_walk_ops show_numa_pgtable_ops = {
> +	.pmd_entry = gather_pgtable_numa_stats,
> +};
> +
> +/*
> + * Display the page talbe allocated per node via /proc.

s/talbe/table/

but the comment somehow doesn't make sense. We don't display a page table.

> + */
> +static int show_numa_pgtable(struct seq_file *m, void *v)
> +{
> +	struct pgtable_numa_private *numa_priv = m->private;
> +	struct vm_area_struct *vma = v;
> +	struct mm_struct *mm = vma->vm_mm;
> +	struct file *file = vma->vm_file;
> +	int nid;
> +
> +	if (!mm)
> +		return 0;
> +
> +	memset(numa_priv->node, 0, sizeof(numa_priv->node));
> +
> +	seq_printf(m, "%08lx ", vma->vm_start);
> +
> +	if (file) {
> +		seq_puts(m, " file=");
> +		seq_file_path(m, file, "\n\t= ");
> +	} else if (vma->vm_start <= mm->brk && vma->vm_end >= mm->start_brk) {
> +		seq_puts(m, " heap");
> +	} else if (is_stack(vma)) {
> +		seq_puts(m, " stack");
> +	}
> +
> +	/* mmap_lock is held by m_start */
> +	walk_page_vma(vma, &show_numa_pgtable_ops, numa_priv);
> +
> +	for_each_node_state(nid, N_MEMORY) {
> +		if (numa_priv->node[nid])
> +			seq_printf(m, " N%d=%lu", nid, numa_priv->node[nid]);
> +	}
> +	seq_putc(m, '\n');
> +
> +	return 0;
> +}
> +
> +static const struct seq_operations proc_pid_numa_pgtable_op = {
> +	.start  = m_start,
> +	.next   = m_next,
> +	.stop   = m_stop,
> +	.show   = show_numa_pgtable,
> +};
> +
> +static int pid_numa_pgtable_open(struct inode *inode, struct file *file)
> +{
> +	return proc_maps_open(inode, file, &proc_pid_numa_pgtable_op,
> +			sizeof(struct pgtable_numa_private));
> +}
> +
> +const struct file_operations proc_pid_numa_pgtable_operations = {
> +	.open		= pid_numa_pgtable_open,
> +	.read		= seq_read,
> +	.llseek		= seq_lseek,
> +	.release	= proc_map_release,
> +};
> +
>  #endif /* CONFIG_NUMA */
> --
> 2.31.0
> 


-- 
Thanks,

David / dhildenb

Re: [RFC PATCH V4 1/1] mm: add last level page table numa info to /proc/pid/numa_pgtable

[haoxin]

在 2022/8/1 下午9:28, David Hildenbrand 写道:
> On 01.08.22 14:17, Xin Hao wrote:
>> In many data center servers, the shared memory architectures is
>> Non-Uniform Memory Access (NUMA), remote numa node data access
>> often brings a high latency problem, but what we are easy to ignore
>> is that the page table remote numa access, It can also leads to a
>> performance degradation.
> Let me try rewriting:
>
> "
> Many data center servers employ Non-Uniform Memory Access (NUMA)
> architectures. Remote numa memory access results in high latency. While
> memory placement is one issue, sub-optimal page table placement can also
> result in surprise performance degradation.
> "
Thanks,  it reads more clearly.

>> So there add a new interface in /proc, This will help developers to
>> get more info about performance issues if they are caused by cross-NUMA.
>
> Why do we only care about "last level page table", why not about the others?
>
> IMHO, we could emit something like "0, 1, 3, 0" instead for a given user
> space address, showing the NUMA node the page table belongs to from
> highest to lowest page table level.

I have planned to implement the PTE page table in this version first,  
and then support other page tables in the next patch later.

>
>> Reported-by: kernel test robot <lkp@intel.com>
> The kernel test robot reported that we need "/proc/pid/numa_pgtable" ?! :)
>
> Just drop that unless it's a follow-up fix.
Get it.
>
>> Signed-off-by: Xin Hao <xhao@linux.alibaba.com>
>> ---
>>   fs/proc/base.c     |  2 ++
>>   fs/proc/internal.h |  1 +
>>   fs/proc/task_mmu.c | 87 ++++++++++++++++++++++++++++++++++++++++++++++
>>   3 files changed, 90 insertions(+)
>>
>> diff --git a/fs/proc/base.c b/fs/proc/base.c
>> index 8dfa36a99c74..487e82dd3275 100644
>> --- a/fs/proc/base.c
>> +++ b/fs/proc/base.c
>> @@ -3224,6 +3224,7 @@ static const struct pid_entry tgid_base_stuff[] = {
>>   	REG("maps",       S_IRUGO, proc_pid_maps_operations),
>>   #ifdef CONFIG_NUMA
>>   	REG("numa_maps",  S_IRUGO, proc_pid_numa_maps_operations),
>> +	REG("numa_pgtable", S_IRUGO, proc_pid_numa_pgtable_operations),
>>   #endif
>>   	REG("mem",        S_IRUSR|S_IWUSR, proc_mem_operations),
>>   	LNK("cwd",        proc_cwd_link),
>> @@ -3571,6 +3572,7 @@ static const struct pid_entry tid_base_stuff[] = {
>>   #endif
>>   #ifdef CONFIG_NUMA
>>   	REG("numa_maps", S_IRUGO, proc_pid_numa_maps_operations),
>> +	REG("numa_pgtable", S_IRUGO, proc_pid_numa_pgtable_operations),
>>   #endif
>>   	REG("mem",       S_IRUSR|S_IWUSR, proc_mem_operations),
>>   	LNK("cwd",       proc_cwd_link),
>> diff --git a/fs/proc/internal.h b/fs/proc/internal.h
>> index 06a80f78433d..e7ed9ef097b6 100644
>> --- a/fs/proc/internal.h
>> +++ b/fs/proc/internal.h
>> @@ -296,6 +296,7 @@ struct mm_struct *proc_mem_open(struct inode *inode, unsigned int mode);
>>
>>   extern const struct file_operations proc_pid_maps_operations;
>>   extern const struct file_operations proc_pid_numa_maps_operations;
>> +extern const struct file_operations proc_pid_numa_pgtable_operations;
>>   extern const struct file_operations proc_pid_smaps_operations;
>>   extern const struct file_operations proc_pid_smaps_rollup_operations;
>>   extern const struct file_operations proc_clear_refs_operations;
>> diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
>> index 2d04e3470d4c..77b7a49757f5 100644
>> --- a/fs/proc/task_mmu.c
>> +++ b/fs/proc/task_mmu.c
>> @@ -1999,4 +1999,91 @@ const struct file_operations proc_pid_numa_maps_operations = {
>>   	.release	= proc_map_release,
>>   };
>>
>> +struct pgtable_numa_private {
>> +	struct proc_maps_private proc_maps;
>> +	unsigned long node[MAX_NUMNODES];
>> +};
>> +
>> +static int gather_pgtable_numa_stats(pmd_t *pmd, unsigned long addr,
>> +				     unsigned long end, struct mm_walk *walk)
>> +{
>> +	struct pgtable_numa_private *priv = walk->private;
>> +	struct page *page;
>> +	int nid;
>> +
>> +	if (pmd_huge(*pmd)) {
>> +		page = virt_to_page(pmd);
>> +	} else {
>> +		page = pmd_page(*pmd);
>> +	}
>> +
>> +	nid = page_to_nid(page);
>> +	priv->node[nid]++;
>> +
>> +	return 0;
>> +}
>> +
>> +static const struct mm_walk_ops show_numa_pgtable_ops = {
>> +	.pmd_entry = gather_pgtable_numa_stats,
>> +};
>> +
>> +/*
>> + * Display the page talbe allocated per node via /proc.
> s/talbe/table/
>
> but the comment somehow doesn't make sense. We don't display a page table.
>
>> + */
>> +static int show_numa_pgtable(struct seq_file *m, void *v)
>> +{
>> +	struct pgtable_numa_private *numa_priv = m->private;
>> +	struct vm_area_struct *vma = v;
>> +	struct mm_struct *mm = vma->vm_mm;
>> +	struct file *file = vma->vm_file;
>> +	int nid;
>> +
>> +	if (!mm)
>> +		return 0;
>> +
>> +	memset(numa_priv->node, 0, sizeof(numa_priv->node));
>> +
>> +	seq_printf(m, "%08lx ", vma->vm_start);
>> +
>> +	if (file) {
>> +		seq_puts(m, " file=");
>> +		seq_file_path(m, file, "\n\t= ");
>> +	} else if (vma->vm_start <= mm->brk && vma->vm_end >= mm->start_brk) {
>> +		seq_puts(m, " heap");
>> +	} else if (is_stack(vma)) {
>> +		seq_puts(m, " stack");
>> +	}
>> +
>> +	/* mmap_lock is held by m_start */
>> +	walk_page_vma(vma, &show_numa_pgtable_ops, numa_priv);
>> +
>> +	for_each_node_state(nid, N_MEMORY) {
>> +		if (numa_priv->node[nid])
>> +			seq_printf(m, " N%d=%lu", nid, numa_priv->node[nid]);
>> +	}
>> +	seq_putc(m, '\n');
>> +
>> +	return 0;
>> +}
>> +
>> +static const struct seq_operations proc_pid_numa_pgtable_op = {
>> +	.start  = m_start,
>> +	.next   = m_next,
>> +	.stop   = m_stop,
>> +	.show   = show_numa_pgtable,
>> +};
>> +
>> +static int pid_numa_pgtable_open(struct inode *inode, struct file *file)
>> +{
>> +	return proc_maps_open(inode, file, &proc_pid_numa_pgtable_op,
>> +			sizeof(struct pgtable_numa_private));
>> +}
>> +
>> +const struct file_operations proc_pid_numa_pgtable_operations = {
>> +	.open		= pid_numa_pgtable_open,
>> +	.read		= seq_read,
>> +	.llseek		= seq_lseek,
>> +	.release	= proc_map_release,
>> +};
>> +
>>   #endif /* CONFIG_NUMA */
>> --
>> 2.31.0
>>
>

Re: [RFC PATCH V4 1/1] mm: add last level page table numa info to /proc/pid/numa_pgtable

[David Hildenbrand]

On 04.08.22 10:04, haoxin wrote:
> 
> 在 2022/8/1 下午9:28, David Hildenbrand 写道:
>> On 01.08.22 14:17, Xin Hao wrote:
>>> In many data center servers, the shared memory architectures is
>>> Non-Uniform Memory Access (NUMA), remote numa node data access
>>> often brings a high latency problem, but what we are easy to ignore
>>> is that the page table remote numa access, It can also leads to a
>>> performance degradation.
>> Let me try rewriting:
>>
>> "
>> Many data center servers employ Non-Uniform Memory Access (NUMA)
>> architectures. Remote numa memory access results in high latency. While
>> memory placement is one issue, sub-optimal page table placement can also
>> result in surprise performance degradation.
>> "
> Thanks,  it reads more clearly.
> 
>>> So there add a new interface in /proc, This will help developers to
>>> get more info about performance issues if they are caused by cross-NUMA.
>>
>> Why do we only care about "last level page table", why not about the others?
>>
>> IMHO, we could emit something like "0, 1, 3, 0" instead for a given user
>> space address, showing the NUMA node the page table belongs to from
>> highest to lowest page table level.
> 
> I have planned to implement the PTE page table in this version first,  
> and then support other page tables in the next patch later.

If there are plans, let's do it all at once, to get a good and single
interface to expose that information.

-- 
Thanks,

David / dhildenb

Re: [RFC PATCH V4 1/1] mm: add last level page table numa info to /proc/pid/numa_pgtable

[haoxin]

在 2022/8/4 下午4:12, David Hildenbrand 写道:
> On 04.08.22 10:04, haoxin wrote:
>> 在 2022/8/1 下午9:28, David Hildenbrand 写道:
>>> On 01.08.22 14:17, Xin Hao wrote:
>>>> In many data center servers, the shared memory architectures is
>>>> Non-Uniform Memory Access (NUMA), remote numa node data access
>>>> often brings a high latency problem, but what we are easy to ignore
>>>> is that the page table remote numa access, It can also leads to a
>>>> performance degradation.
>>> Let me try rewriting:
>>>
>>> "
>>> Many data center servers employ Non-Uniform Memory Access (NUMA)
>>> architectures. Remote numa memory access results in high latency. While
>>> memory placement is one issue, sub-optimal page table placement can also
>>> result in surprise performance degradation.
>>> "
>> Thanks,  it reads more clearly.
>>
>>>> So there add a new interface in /proc, This will help developers to
>>>> get more info about performance issues if they are caused by cross-NUMA.
>>> Why do we only care about "last level page table", why not about the others?
>>>
>>> IMHO, we could emit something like "0, 1, 3, 0" instead for a given user
>>> space address, showing the NUMA node the page table belongs to from
>>> highest to lowest page table level.
>> I have planned to implement the PTE page table in this version first,
>> and then support other page tables in the next patch later.
> If there are plans, let's do it all at once, to get a good and single
> interface to expose that information.
Ok, thanks for your suggestion, I will implement it in the next version.

>