[PATCH] mm/alloc_tag: add the ARCH_NEEDS_WEAK_PER_CPU macro when statically defining the percpu variable alloc_tag_counters.

[PATCH] mm/alloc_tag: add the ARCH_NEEDS_WEAK_PER_CPU macro when statically defining the percpu variable alloc_tag_counters.

[Hao Ge]

From: Hao Ge <gehao@kylinos.cn>

Recently discovered this entry while checking kallsyms on ARM64:
ffff800083e509c0 D _shared_alloc_tag

If ARCH_NEEDS_WEAK_PER_CPU is not defined,there's no need to statically
define the percpu variable alloc_tag_counters.

Therefore,add therelevant macro guards at the appropriate location.

Fixes: 22d407b164ff ("lib: add allocation tagging support for memory allocation profiling")
Signed-off-by: Hao Ge <gehao@kylinos.cn>
---
 lib/alloc_tag.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/lib/alloc_tag.c b/lib/alloc_tag.c
index c7f602fa7b23..d1dab80b70ad 100644
--- a/lib/alloc_tag.c
+++ b/lib/alloc_tag.c
@@ -24,8 +24,10 @@ static bool mem_profiling_support;
 
 static struct codetag_type *alloc_tag_cttype;
 
+#ifdef ARCH_NEEDS_WEAK_PER_CPU
 DEFINE_PER_CPU(struct alloc_tag_counters, _shared_alloc_tag);
 EXPORT_SYMBOL(_shared_alloc_tag);
+#endif /* ARCH_NEEDS_WEAK_PER_CPU */
 
 DEFINE_STATIC_KEY_MAYBE(CONFIG_MEM_ALLOC_PROFILING_ENABLED_BY_DEFAULT,
 			mem_alloc_profiling_key);
-- 
2.25.1

Re: [PATCH] mm/alloc_tag: add the ARCH_NEEDS_WEAK_PER_CPU macro when statically defining the percpu variable alloc_tag_counters.

[Hao Ge]

On 2025/5/29 15:35, Hao Ge wrote:
> From: Hao Ge <gehao@kylinos.cn>
>
> Recently discovered this entry while checking kallsyms on ARM64:
> ffff800083e509c0 D _shared_alloc_tag
>
> If ARCH_NEEDS_WEAK_PER_CPU is not defined,there's no need to statically
> define the percpu variable alloc_tag_counters.
>
> Therefore,add therelevant macro guards at the appropriate location.
>
> Fixes: 22d407b164ff ("lib: add allocation tagging support for memory allocation profiling")
> Signed-off-by: Hao Ge <gehao@kylinos.cn>
> ---
>   lib/alloc_tag.c | 2 ++
>   1 file changed, 2 insertions(+)
>
> diff --git a/lib/alloc_tag.c b/lib/alloc_tag.c
> index c7f602fa7b23..d1dab80b70ad 100644
> --- a/lib/alloc_tag.c
> +++ b/lib/alloc_tag.c
> @@ -24,8 +24,10 @@ static bool mem_profiling_support;
>   
>   static struct codetag_type *alloc_tag_cttype;
>   
> +#ifdef ARCH_NEEDS_WEAK_PER_CPU
>   DEFINE_PER_CPU(struct alloc_tag_counters, _shared_alloc_tag);
>   EXPORT_SYMBOL(_shared_alloc_tag);
> +#endif /* ARCH_NEEDS_WEAK_PER_CPU */
>   
>   DEFINE_STATIC_KEY_MAYBE(CONFIG_MEM_ALLOC_PROFILING_ENABLED_BY_DEFAULT,
>   			mem_alloc_profiling_key);

Hi Suren


I'm sorry to bother you. As mentioned in my commit message,

in fact, on the ARM64 architecture, the _shared_alloc_tag percpu 
variable is not needed.

In my understanding, it will create a copy for each CPU.

  The alloc_tag_counters variable will occupy 16 bytes,

and as the number of CPUs increases, more and more memory will be wasted 
in this segment.

I realized that this modification was a mistake. It resulted in a build 
error, and the link is as follows:

https://lore.kernel.org/all/202506080448.KWN8arrX-lkp@intel.com/

After I studied the comments of DECLARE_PER_CPU_SECTION, I roughly 
understood why this is the case.

But so far, I haven't come up with a good way to solve this problem. Do 
you have any suggestions?


Thanks

Best Regards

Hao

Re: [PATCH] mm/alloc_tag: add the ARCH_NEEDS_WEAK_PER_CPU macro when statically defining the percpu variable alloc_tag_counters.

[Suren Baghdasaryan]

On Sun, Jun 8, 2025 at 11:08 PM Hao Ge <hao.ge@linux.dev> wrote:
>
>
> On 2025/5/29 15:35, Hao Ge wrote:
> > From: Hao Ge <gehao@kylinos.cn>
> >
> > Recently discovered this entry while checking kallsyms on ARM64:
> > ffff800083e509c0 D _shared_alloc_tag
> >
> > If ARCH_NEEDS_WEAK_PER_CPU is not defined,there's no need to statically
> > define the percpu variable alloc_tag_counters.
> >
> > Therefore,add therelevant macro guards at the appropriate location.
> >
> > Fixes: 22d407b164ff ("lib: add allocation tagging support for memory allocation profiling")
> > Signed-off-by: Hao Ge <gehao@kylinos.cn>
> > ---
> >   lib/alloc_tag.c | 2 ++
> >   1 file changed, 2 insertions(+)
> >
> > diff --git a/lib/alloc_tag.c b/lib/alloc_tag.c
> > index c7f602fa7b23..d1dab80b70ad 100644
> > --- a/lib/alloc_tag.c
> > +++ b/lib/alloc_tag.c
> > @@ -24,8 +24,10 @@ static bool mem_profiling_support;
> >
> >   static struct codetag_type *alloc_tag_cttype;
> >
> > +#ifdef ARCH_NEEDS_WEAK_PER_CPU
> >   DEFINE_PER_CPU(struct alloc_tag_counters, _shared_alloc_tag);
> >   EXPORT_SYMBOL(_shared_alloc_tag);
> > +#endif /* ARCH_NEEDS_WEAK_PER_CPU */
> >
> >   DEFINE_STATIC_KEY_MAYBE(CONFIG_MEM_ALLOC_PROFILING_ENABLED_BY_DEFAULT,
> >                       mem_alloc_profiling_key);
>
> Hi Suren
>
>
> I'm sorry to bother you. As mentioned in my commit message,
>
> in fact, on the ARM64 architecture, the _shared_alloc_tag percpu
> variable is not needed.
>
> In my understanding, it will create a copy for each CPU.
>
>   The alloc_tag_counters variable will occupy 16 bytes,
>
> and as the number of CPUs increases, more and more memory will be wasted
> in this segment.
>
> I realized that this modification was a mistake. It resulted in a build
> error, and the link is as follows:
>
> https://lore.kernel.org/all/202506080448.KWN8arrX-lkp@intel.com/
>
> After I studied the comments of DECLARE_PER_CPU_SECTION, I roughly
> understood why this is the case.
>
> But so far, I haven't come up with a good way to solve this problem. Do
> you have any suggestions?

Hi Hao,
The problem here is that ARCH_NEEDS_WEAK_PER_CPU is not a Kconfig
option, it gets defined only on 2 architectures and only when building
modules here https://elixir.bootlin.com/linux/v6.15.1/source/arch/alpha/include/asm/percpu.h#L14
and here https://elixir.bootlin.com/linux/v6.15.1/source/arch/s390/include/asm/percpu.h#L21.
A nicer way to deal with that is to make if a Kconfig option which is
enabled only for alpha and s390 and then do something like this:

 #if defined(MODULE) && defined(ARCH_NEEDS_WEAK_PER_CPU)
#define MODULE_NEEDS_WEAK_PER_CPU
#endif

and change all the usages of ARCH_NEEDS_WEAK_PER_CPU with
MODULE_NEEDS_WEAK_PER_CPU.
Did I explain the idea clearly?
Thanks,
Suren.


>
>
> Thanks
>
> Best Regards
>
> Hao
>
>
>
>

Re: [PATCH] mm/alloc_tag: add the ARCH_NEEDS_WEAK_PER_CPU macro when statically defining the percpu variable alloc_tag_counters.

[Hao Ge]

On 2025/6/10 00:39, Suren Baghdasaryan wrote:
> On Sun, Jun 8, 2025 at 11:08 PM Hao Ge <hao.ge@linux.dev> wrote:
>>
>> On 2025/5/29 15:35, Hao Ge wrote:
>>> From: Hao Ge <gehao@kylinos.cn>
>>>
>>> Recently discovered this entry while checking kallsyms on ARM64:
>>> ffff800083e509c0 D _shared_alloc_tag
>>>
>>> If ARCH_NEEDS_WEAK_PER_CPU is not defined,there's no need to statically
>>> define the percpu variable alloc_tag_counters.
>>>
>>> Therefore,add therelevant macro guards at the appropriate location.
>>>
>>> Fixes: 22d407b164ff ("lib: add allocation tagging support for memory allocation profiling")
>>> Signed-off-by: Hao Ge <gehao@kylinos.cn>
>>> ---
>>>    lib/alloc_tag.c | 2 ++
>>>    1 file changed, 2 insertions(+)
>>>
>>> diff --git a/lib/alloc_tag.c b/lib/alloc_tag.c
>>> index c7f602fa7b23..d1dab80b70ad 100644
>>> --- a/lib/alloc_tag.c
>>> +++ b/lib/alloc_tag.c
>>> @@ -24,8 +24,10 @@ static bool mem_profiling_support;
>>>
>>>    static struct codetag_type *alloc_tag_cttype;
>>>
>>> +#ifdef ARCH_NEEDS_WEAK_PER_CPU
>>>    DEFINE_PER_CPU(struct alloc_tag_counters, _shared_alloc_tag);
>>>    EXPORT_SYMBOL(_shared_alloc_tag);
>>> +#endif /* ARCH_NEEDS_WEAK_PER_CPU */
>>>
>>>    DEFINE_STATIC_KEY_MAYBE(CONFIG_MEM_ALLOC_PROFILING_ENABLED_BY_DEFAULT,
>>>                        mem_alloc_profiling_key);
>> Hi Suren
>>
>>
>> I'm sorry to bother you. As mentioned in my commit message,
>>
>> in fact, on the ARM64 architecture, the _shared_alloc_tag percpu
>> variable is not needed.
>>
>> In my understanding, it will create a copy for each CPU.
>>
>>    The alloc_tag_counters variable will occupy 16 bytes,
>>
>> and as the number of CPUs increases, more and more memory will be wasted
>> in this segment.
>>
>> I realized that this modification was a mistake. It resulted in a build
>> error, and the link is as follows:
>>
>> https://lore.kernel.org/all/202506080448.KWN8arrX-lkp@intel.com/
>>
>> After I studied the comments of DECLARE_PER_CPU_SECTION, I roughly
>> understood why this is the case.
>>
>> But so far, I haven't come up with a good way to solve this problem. Do
>> you have any suggestions?
> Hi Hao,
> The problem here is that ARCH_NEEDS_WEAK_PER_CPU is not a Kconfig
> option, it gets defined only on 2 architectures and only when building
> modules here https://elixir.bootlin.com/linux/v6.15.1/source/arch/alpha/include/asm/percpu.h#L14
> and here https://elixir.bootlin.com/linux/v6.15.1/source/arch/s390/include/asm/percpu.h#L21.
> A nicer way to deal with that is to make if a Kconfig option which is
> enabled only for alpha and s390 and then do something like this:
>
>   #if defined(MODULE) && defined(ARCH_NEEDS_WEAK_PER_CPU)
> #define MODULE_NEEDS_WEAK_PER_CPU
> #endif
>
> and change all the usages of ARCH_NEEDS_WEAK_PER_CPU with
> MODULE_NEEDS_WEAK_PER_CPU.
> Did I explain the idea clearly?
> Thanks,
> Suren.
>
Hi Suren

Thanks for your guidance.
I understand this train of thought.

I've been thinking about a problem: I only added the 
ARCH_NEEDS_WEAK_PER_CPU

macro to isolate the definition of _shared_alloc_tag.

Since s390 defines this macro, why did this build error occur?

Could you please help explain it again?

Thanks
Best Regards
Hao

>>
>> Thanks
>>
>> Best Regards
>>
>> Hao
>>
>>
>>
>>

Re: [PATCH] mm/alloc_tag: add the ARCH_NEEDS_WEAK_PER_CPU macro when statically defining the percpu variable alloc_tag_counters.

[Suren Baghdasaryan]

On Tue, Jun 10, 2025 at 10:27 PM Hao Ge <hao.ge@linux.dev> wrote:
>
>
> On 2025/6/10 00:39, Suren Baghdasaryan wrote:
> > On Sun, Jun 8, 2025 at 11:08 PM Hao Ge <hao.ge@linux.dev> wrote:
> >>
> >> On 2025/5/29 15:35, Hao Ge wrote:
> >>> From: Hao Ge <gehao@kylinos.cn>
> >>>
> >>> Recently discovered this entry while checking kallsyms on ARM64:
> >>> ffff800083e509c0 D _shared_alloc_tag
> >>>
> >>> If ARCH_NEEDS_WEAK_PER_CPU is not defined,there's no need to statically
> >>> define the percpu variable alloc_tag_counters.
> >>>
> >>> Therefore,add therelevant macro guards at the appropriate location.
> >>>
> >>> Fixes: 22d407b164ff ("lib: add allocation tagging support for memory allocation profiling")
> >>> Signed-off-by: Hao Ge <gehao@kylinos.cn>
> >>> ---
> >>>    lib/alloc_tag.c | 2 ++
> >>>    1 file changed, 2 insertions(+)
> >>>
> >>> diff --git a/lib/alloc_tag.c b/lib/alloc_tag.c
> >>> index c7f602fa7b23..d1dab80b70ad 100644
> >>> --- a/lib/alloc_tag.c
> >>> +++ b/lib/alloc_tag.c
> >>> @@ -24,8 +24,10 @@ static bool mem_profiling_support;
> >>>
> >>>    static struct codetag_type *alloc_tag_cttype;
> >>>
> >>> +#ifdef ARCH_NEEDS_WEAK_PER_CPU
> >>>    DEFINE_PER_CPU(struct alloc_tag_counters, _shared_alloc_tag);
> >>>    EXPORT_SYMBOL(_shared_alloc_tag);
> >>> +#endif /* ARCH_NEEDS_WEAK_PER_CPU */
> >>>
> >>>    DEFINE_STATIC_KEY_MAYBE(CONFIG_MEM_ALLOC_PROFILING_ENABLED_BY_DEFAULT,
> >>>                        mem_alloc_profiling_key);
> >> Hi Suren
> >>
> >>
> >> I'm sorry to bother you. As mentioned in my commit message,
> >>
> >> in fact, on the ARM64 architecture, the _shared_alloc_tag percpu
> >> variable is not needed.
> >>
> >> In my understanding, it will create a copy for each CPU.
> >>
> >>    The alloc_tag_counters variable will occupy 16 bytes,
> >>
> >> and as the number of CPUs increases, more and more memory will be wasted
> >> in this segment.
> >>
> >> I realized that this modification was a mistake. It resulted in a build
> >> error, and the link is as follows:
> >>
> >> https://lore.kernel.org/all/202506080448.KWN8arrX-lkp@intel.com/
> >>
> >> After I studied the comments of DECLARE_PER_CPU_SECTION, I roughly
> >> understood why this is the case.
> >>
> >> But so far, I haven't come up with a good way to solve this problem. Do
> >> you have any suggestions?
> > Hi Hao,
> > The problem here is that ARCH_NEEDS_WEAK_PER_CPU is not a Kconfig
> > option, it gets defined only on 2 architectures and only when building
> > modules here https://elixir.bootlin.com/linux/v6.15.1/source/arch/alpha/include/asm/percpu.h#L14
> > and here https://elixir.bootlin.com/linux/v6.15.1/source/arch/s390/include/asm/percpu.h#L21.
> > A nicer way to deal with that is to make if a Kconfig option which is
> > enabled only for alpha and s390 and then do something like this:
> >
> >   #if defined(MODULE) && defined(ARCH_NEEDS_WEAK_PER_CPU)
> > #define MODULE_NEEDS_WEAK_PER_CPU
> > #endif
> >
> > and change all the usages of ARCH_NEEDS_WEAK_PER_CPU with
> > MODULE_NEEDS_WEAK_PER_CPU.
> > Did I explain the idea clearly?
> > Thanks,
> > Suren.
> >
> Hi Suren

Hi Hao,

>
> Thanks for your guidance.
> I understand this train of thought.
>
> I've been thinking about a problem: I only added the
> ARCH_NEEDS_WEAK_PER_CPU
>
> macro to isolate the definition of _shared_alloc_tag.
>
> Since s390 defines this macro, why did this build error occur?

The problem is that ARCH_NEEDS_WEAK_PER_CPU is not a Kconfig option,
it's just a definition, for s390 it's here:
https://elixir.bootlin.com/linux/v6.15.1/source/arch/s390/include/asm/percpu.h#L21
So, even for s390 if you are building core kernel code (not a module),
ARCH_NEEDS_WEAK_PER_CPU will be undefined, however if you are building
a module on s390 then it is defined. So, your change effectively
results in _shared_alloc_tag being compiled out in the core kernel
while it's used when you build a module. Therefore during linking
modules can't link to that symbol in the core kernel. Hope this
explains the issue.

The way I would fix this is by making ARCH_NEEDS_WEAK_PER_CPU a
Kconfig option and enable it for s390 and alpha, would replace old
definitions from
https://elixir.bootlin.com/linux/v6.15.1/source/arch/s390/include/asm/percpu.h#L21
and https://elixir.bootlin.com/linux/v6.15.1/source/arch/alpha/include/asm/percpu.h#L14
with:

#if defined(MODULE) && defined(ARCH_NEEDS_WEAK_PER_CPU)
#define MODULE_NEEDS_WEAK_PER_CPU
#endif

Then use MODULE_NEEDS_WEAK_PER_CPU instead of ARCH_NEEDS_WEAK_PER_CPU
in all the current places in the kernel code. Lastly, to compile out
_shared_alloc_tag your current patch should work fine because on s390
and alpha ARCH_NEEDS_WEAK_PER_CPU will be defined after all these
changes.
Does that make sense?

>
> Could you please help explain it again?
>
> Thanks
> Best Regards
> Hao
>
> >>
> >> Thanks
> >>
> >> Best Regards
> >>
> >> Hao
> >>
> >>
> >>
> >>

Re: [PATCH] mm/alloc_tag: add the ARCH_NEEDS_WEAK_PER_CPU macro when statically defining the percpu variable alloc_tag_counters.

[Hao Ge]

On 2025/6/11 23:24, Suren Baghdasaryan wrote:
> On Tue, Jun 10, 2025 at 10:27 PM Hao Ge <hao.ge@linux.dev> wrote:
>>
>> On 2025/6/10 00:39, Suren Baghdasaryan wrote:
>>> On Sun, Jun 8, 2025 at 11:08 PM Hao Ge <hao.ge@linux.dev> wrote:
>>>> On 2025/5/29 15:35, Hao Ge wrote:
>>>>> From: Hao Ge <gehao@kylinos.cn>
>>>>>
>>>>> Recently discovered this entry while checking kallsyms on ARM64:
>>>>> ffff800083e509c0 D _shared_alloc_tag
>>>>>
>>>>> If ARCH_NEEDS_WEAK_PER_CPU is not defined,there's no need to statically
>>>>> define the percpu variable alloc_tag_counters.
>>>>>
>>>>> Therefore,add therelevant macro guards at the appropriate location.
>>>>>
>>>>> Fixes: 22d407b164ff ("lib: add allocation tagging support for memory allocation profiling")
>>>>> Signed-off-by: Hao Ge <gehao@kylinos.cn>
>>>>> ---
>>>>>     lib/alloc_tag.c | 2 ++
>>>>>     1 file changed, 2 insertions(+)
>>>>>
>>>>> diff --git a/lib/alloc_tag.c b/lib/alloc_tag.c
>>>>> index c7f602fa7b23..d1dab80b70ad 100644
>>>>> --- a/lib/alloc_tag.c
>>>>> +++ b/lib/alloc_tag.c
>>>>> @@ -24,8 +24,10 @@ static bool mem_profiling_support;
>>>>>
>>>>>     static struct codetag_type *alloc_tag_cttype;
>>>>>
>>>>> +#ifdef ARCH_NEEDS_WEAK_PER_CPU
>>>>>     DEFINE_PER_CPU(struct alloc_tag_counters, _shared_alloc_tag);
>>>>>     EXPORT_SYMBOL(_shared_alloc_tag);
>>>>> +#endif /* ARCH_NEEDS_WEAK_PER_CPU */
>>>>>
>>>>>     DEFINE_STATIC_KEY_MAYBE(CONFIG_MEM_ALLOC_PROFILING_ENABLED_BY_DEFAULT,
>>>>>                         mem_alloc_profiling_key);
>>>> Hi Suren
>>>>
>>>>
>>>> I'm sorry to bother you. As mentioned in my commit message,
>>>>
>>>> in fact, on the ARM64 architecture, the _shared_alloc_tag percpu
>>>> variable is not needed.
>>>>
>>>> In my understanding, it will create a copy for each CPU.
>>>>
>>>>     The alloc_tag_counters variable will occupy 16 bytes,
>>>>
>>>> and as the number of CPUs increases, more and more memory will be wasted
>>>> in this segment.
>>>>
>>>> I realized that this modification was a mistake. It resulted in a build
>>>> error, and the link is as follows:
>>>>
>>>> https://lore.kernel.org/all/202506080448.KWN8arrX-lkp@intel.com/
>>>>
>>>> After I studied the comments of DECLARE_PER_CPU_SECTION, I roughly
>>>> understood why this is the case.
>>>>
>>>> But so far, I haven't come up with a good way to solve this problem. Do
>>>> you have any suggestions?
>>> Hi Hao,
>>> The problem here is that ARCH_NEEDS_WEAK_PER_CPU is not a Kconfig
>>> option, it gets defined only on 2 architectures and only when building
>>> modules here https://elixir.bootlin.com/linux/v6.15.1/source/arch/alpha/include/asm/percpu.h#L14
>>> and here https://elixir.bootlin.com/linux/v6.15.1/source/arch/s390/include/asm/percpu.h#L21.
>>> A nicer way to deal with that is to make if a Kconfig option which is
>>> enabled only for alpha and s390 and then do something like this:
>>>
>>>    #if defined(MODULE) && defined(ARCH_NEEDS_WEAK_PER_CPU)
>>> #define MODULE_NEEDS_WEAK_PER_CPU
>>> #endif
>>>
>>> and change all the usages of ARCH_NEEDS_WEAK_PER_CPU with
>>> MODULE_NEEDS_WEAK_PER_CPU.
>>> Did I explain the idea clearly?
>>> Thanks,
>>> Suren.
>>>
>> Hi Suren
> Hi Hao,
>
>> Thanks for your guidance.
>> I understand this train of thought.
>>
>> I've been thinking about a problem: I only added the
>> ARCH_NEEDS_WEAK_PER_CPU
>>
>> macro to isolate the definition of _shared_alloc_tag.
>>
>> Since s390 defines this macro, why did this build error occur?
Hi Suren
> The problem is that ARCH_NEEDS_WEAK_PER_CPU is not a Kconfig option,
> it's just a definition, for s390 it's here:
> https://elixir.bootlin.com/linux/v6.15.1/source/arch/s390/include/asm/percpu.h#L21
> So, even for s390 if you are building core kernel code (not a module),
> ARCH_NEEDS_WEAK_PER_CPU will be undefined, however if you are building
> a module on s390 then it is defined. So, your change effectively
> results in _shared_alloc_tag being compiled out in the core kernel
> while it's used when you build a module. Therefore during linking
> modules can't link to that symbol in the core kernel. Hope this
> explains the issue.


Thank you so, so, so much! I understand now, and thank you for such a 
detailed explanation.


> The way I would fix this is by making ARCH_NEEDS_WEAK_PER_CPU a
> Kconfig option and enable it for s390 and alpha, would replace old
> definitions from
> https://elixir.bootlin.com/linux/v6.15.1/source/arch/s390/include/asm/percpu.h#L21
> and https://elixir.bootlin.com/linux/v6.15.1/source/arch/alpha/include/asm/percpu.h#L14
> with:
>
> #if defined(MODULE) && defined(ARCH_NEEDS_WEAK_PER_CPU)
> #define MODULE_NEEDS_WEAK_PER_CPU
> #endif
>
> Then use MODULE_NEEDS_WEAK_PER_CPU instead of ARCH_NEEDS_WEAK_PER_CPU
> in all the current places in the kernel code. Lastly, to compile out
> _shared_alloc_tag your current patch should work fine because on s390
> and alpha ARCH_NEEDS_WEAK_PER_CPU will be defined after all these
> changes.
> Does that make sense?


I quite agree with this approach.

Thanks
Best Regards
Hao

>> Could you please help explain it again?
>>
>> Thanks
>> Best Regards
>> Hao
>>
>>>> Thanks
>>>>
>>>> Best Regards
>>>>
>>>> Hao
>>>>
>>>>
>>>>
>>>>