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Re: [PATCH 2/2] memory-hotplug: remove reset_node_managed_pages() and reset_node_managed_pages() in hotadd_new_pgdat()

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  Re: [PATCH 2/2] memory-hotplug: remove reset_node_managed_pages()  and reset_node_managed_pages() in hotadd_new_pgdat() Tang Chen <tangchen@cn.fujitsu.com> - 2015-08-23 12:40 +0200
    Re: [PATCH 2/2] memory-hotplug: remove reset_node_managed_pages()  and reset_node_managed_pages() in hotadd_new_pgdat() Xishi Qiu <qiuxishi@huawei.com> - 2015-08-24 11:20 +0200
      Re: [PATCH 2/2] memory-hotplug: remove reset_node_managed_pages()  and reset_node_managed_pages() in hotadd_new_pgdat() Tang Chen <tangchen@cn.fujitsu.com> - 2015-08-24 11:50 +0200
        Re: [PATCH 2/2] memory-hotplug: remove reset_node_managed_pages()  and reset_node_managed_pages() in hotadd_new_pgdat() Xishi Qiu <qiuxishi@huawei.com> - 2015-08-24 13:30 +0200
          Re: [PATCH 2/2] memory-hotplug: remove reset_node_managed_pages()  and reset_node_managed_pages() in hotadd_new_pgdat() Tang Chen <tangchen@cn.fujitsu.com> - 2015-08-26 09:30 +0200

#1211578 — Re: [PATCH 2/2] memory-hotplug: remove reset_node_managed_pages() and reset_node_managed_pages() in hotadd_new_pgdat()

Hi Shi,

Sorry for the late reply. I hope it won't be too late.

NON-ACK by me, I think.

I noticed that your first has been merged. But it won't fix the problem
these code intended to fix.

After your patch 1, zone's spanned/present won't be set to 0 because:

free_area_init_node()
  |--> get_pfn_range_for_nid(&start_pfn, &end_pfn)
  |--> calculate_node_totalpages(pgdat, start_pfn, end_pfn, ...)
          | --> zone_spanned_pages_in_node()
                   | --> if (!node_start_pfn && !node_end_pfn) return 
0;    --------    false, won't return 0
          | --> zone_absent_pages_in_node()
                   | --> if (!node_start_pfn && !node_end_pfn) return 
0;    --------    false, won't return 0

This is caused by a little bug in your patch 1.

You should put memblock_add_node(start, size, nid) before 
hotadd_new_pgdat()
because:

hotadd_new_pgdat()
  | --> free_area_init_node()
           | --> get_pfn_range_for_nid()
                    | --> find memory ranges in memblock.

| --> memblock_add_node(start, size, nid) -------------------    if you 
add it here, it doesn't work.

The result will be like below if we hotadd node 5.
[ 2007.577000] Initmem setup node 5 [mem 
0x0000000000000000-0xffffffffffffffff]
[ 2007.584000] On node 5 totalpages: 0
[ 2007.585000] Built 5 zonelists in Node order, mobility grouping on.  
Total pages: 32588823
[ 2007.594000] Policy zone: Normal
[ 2007.598000] init_memory_mapping: [mem 0x60000000000-0x607ffffffff]


And also, if we merge this patch, /sys/devices/system/node/nodeX/meminfo 
will break.


Since this patch is not merged, I think let's just drop it.

And about the little bug in your patch 1, since I'm in a hurry, I have 
already send a patch to fix it.


Thanks. :)


On 08/11/2015 03:33 PM, Xishi Qiu wrote:
> After hotadd_new_pgdat()->free_area_init_node(), the pgdat and zone's spanned/present
> are both 0, so remove reset_node_managed_pages() and reset_node_managed_pages().
>
> Signed-off-by: Xishi Qiu <qiuxishi@huawei.com>
> ---
>   mm/memory_hotplug.c | 25 -------------------------
>   1 file changed, 25 deletions(-)
>
> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
> index 11f26cc..997dfad 100644
> --- a/mm/memory_hotplug.c
> +++ b/mm/memory_hotplug.c
> @@ -1065,16 +1065,6 @@ int __ref online_pages(unsigned long pfn, unsigned long nr_pages, int online_typ
>   }
>   #endif /* CONFIG_MEMORY_HOTPLUG_SPARSE */
>   
> -static void reset_node_present_pages(pg_data_t *pgdat)
> -{
> -	struct zone *z;
> -
> -	for (z = pgdat->node_zones; z < pgdat->node_zones + MAX_NR_ZONES; z++)
> -		z->present_pages = 0;
> -
> -	pgdat->node_present_pages = 0;
> -}
> -
>   /* we are OK calling __meminit stuff here - we have CONFIG_MEMORY_HOTPLUG */
>   static pg_data_t __ref *hotadd_new_pgdat(int nid, u64 start)
>   {
> @@ -1109,21 +1099,6 @@ static pg_data_t __ref *hotadd_new_pgdat(int nid, u64 start)
>   	build_all_zonelists(pgdat, NULL);
>   	mutex_unlock(&zonelists_mutex);
>   
> -	/*
> -	 * zone->managed_pages is set to an approximate value in
> -	 * free_area_init_core(), which will cause
> -	 * /sys/device/system/node/nodeX/meminfo has wrong data.
> -	 * So reset it to 0 before any memory is onlined.
> -	 */
> -	reset_node_managed_pages(pgdat);
> -
> -	/*
> -	 * When memory is hot-added, all the memory is in offline state. So
> -	 * clear all zones' present_pages because they will be updated in
> -	 * online_pages() and offline_pages().
> -	 */
> -	reset_node_present_pages(pgdat);
> -
>   	return pgdat;
>   }
>   

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#1211964

On 2015/8/23 18:28, Tang Chen wrote:

> Hi Shi,
> 
> Sorry for the late reply. I hope it won't be too late.
> 
> NON-ACK by me, I think.
> 
> I noticed that your first has been merged. But it won't fix the problem
> these code intended to fix.
> 
> After your patch 1, zone's spanned/present won't be set to 0 because:
> 
> free_area_init_node()
>  |--> get_pfn_range_for_nid(&start_pfn, &end_pfn)
>  |--> calculate_node_totalpages(pgdat, start_pfn, end_pfn, ...)
>          | --> zone_spanned_pages_in_node()
>                   | --> if (!node_start_pfn && !node_end_pfn) return 0;    --------    false, won't return 0
>          | --> zone_absent_pages_in_node()
>                   | --> if (!node_start_pfn && !node_end_pfn) return 0;    --------    false, won't return 0
> 

Hi Tang,

Thank you for your reply. When we add a new node, it is not included in the
memblock, I have no idea why zone_spanned_pages_in_node() and zone_absent_pages_in_node()
won't return 0. Do you add some debug code and print it?

> This is caused by a little bug in your patch 1.
> 
> You should put memblock_add_node(start, size, nid) before hotadd_new_pgdat()
> because:
> 

My patch is just add an empty node first, later __add_zone() will update the size.
But it is all right put here, and it can fix the print bug.

> hotadd_new_pgdat()
>  | --> free_area_init_node()
>           | --> get_pfn_range_for_nid()
>                    | --> find memory ranges in memblock.
> 
> | --> memblock_add_node(start, size, nid) -------------------    if you add it here, it doesn't work.
> 
> The result will be like below if we hotadd node 5.
> [ 2007.577000] Initmem setup node 5 [mem 0x0000000000000000-0xffffffffffffffff]

	pr_info("Initmem setup node %d [mem %#018Lx-%#018Lx]\n", nid,
		(u64)start_pfn << PAGE_SHIFT, ((u64)end_pfn << PAGE_SHIFT) - 1);
start_pfn and end_pfn are both 0, and 0-1 -> 0xffffffffffffffff, right?

> [ 2007.584000] On node 5 totalpages: 0
> [ 2007.585000] Built 5 zonelists in Node order, mobility grouping on.  Total pages: 32588823
> [ 2007.594000] Policy zone: Normal
> [ 2007.598000] init_memory_mapping: [mem 0x60000000000-0x607ffffffff]
> 
> 
> And also, if we merge this patch, /sys/devices/system/node/nodeX/meminfo will break.
> 

trigger call trace?

> 
> Since this patch is not merged, I think let's just drop it.
> 
> And about the little bug in your patch 1, since I'm in a hurry, I have already send a patch to fix it.
> 
> 
> Thanks. :)
> 
> 
> On 08/11/2015 03:33 PM, Xishi Qiu wrote:
>> After hotadd_new_pgdat()->free_area_init_node(), the pgdat and zone's spanned/present
>> are both 0, so remove reset_node_managed_pages() and reset_node_managed_pages().
>>
>> Signed-off-by: Xishi Qiu <qiuxishi@huawei.com>
>> ---
>>   mm/memory_hotplug.c | 25 -------------------------
>>   1 file changed, 25 deletions(-)
>>
>> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
>> index 11f26cc..997dfad 100644
>> --- a/mm/memory_hotplug.c
>> +++ b/mm/memory_hotplug.c
>> @@ -1065,16 +1065,6 @@ int __ref online_pages(unsigned long pfn, unsigned long nr_pages, int online_typ
>>   }
>>   #endif /* CONFIG_MEMORY_HOTPLUG_SPARSE */
>>   -static void reset_node_present_pages(pg_data_t *pgdat)
>> -{
>> -    struct zone *z;
>> -
>> -    for (z = pgdat->node_zones; z < pgdat->node_zones + MAX_NR_ZONES; z++)
>> -        z->present_pages = 0;
>> -
>> -    pgdat->node_present_pages = 0;
>> -}
>> -
>>   /* we are OK calling __meminit stuff here - we have CONFIG_MEMORY_HOTPLUG */
>>   static pg_data_t __ref *hotadd_new_pgdat(int nid, u64 start)
>>   {
>> @@ -1109,21 +1099,6 @@ static pg_data_t __ref *hotadd_new_pgdat(int nid, u64 start)
>>       build_all_zonelists(pgdat, NULL);
>>       mutex_unlock(&zonelists_mutex);
>>   -    /*
>> -     * zone->managed_pages is set to an approximate value in
>> -     * free_area_init_core(), which will cause
>> -     * /sys/device/system/node/nodeX/meminfo has wrong data.
>> -     * So reset it to 0 before any memory is onlined.
>> -     */
>> -    reset_node_managed_pages(pgdat);
>> -
>> -    /*
>> -     * When memory is hot-added, all the memory is in offline state. So
>> -     * clear all zones' present_pages because they will be updated in
>> -     * online_pages() and offline_pages().
>> -     */
>> -    reset_node_present_pages(pgdat);
>> -
>>       return pgdat;
>>   }
>>   
> 
> 
> .
> 



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#1212039

On 08/24/2015 05:17 PM, Xishi Qiu wrote:
> On 2015/8/23 18:28, Tang Chen wrote:
>
>> Hi Shi,
>>
>> Sorry for the late reply. I hope it won't be too late.
>>
>> NON-ACK by me, I think.
>>
>> I noticed that your first has been merged. But it won't fix the problem
>> these code intended to fix.
>>
>> After your patch 1, zone's spanned/present won't be set to 0 because:
>>
>> free_area_init_node()
>>   |--> get_pfn_range_for_nid(&start_pfn, &end_pfn)
>>   |--> calculate_node_totalpages(pgdat, start_pfn, end_pfn, ...)
>>           | --> zone_spanned_pages_in_node()
>>                    | --> if (!node_start_pfn && !node_end_pfn) return 0;    --------    false, won't return 0
>>           | --> zone_absent_pages_in_node()
>>                    | --> if (!node_start_pfn && !node_end_pfn) return 0;    --------    false, won't return 0
>>
> Hi Tang,
>
> Thank you for your reply. When we add a new node, it is not included in the
> memblock, I have no idea why zone_spanned_pages_in_node() and zone_absent_pages_in_node()
> won't return 0. Do you add some debug code and print it?

Sorry, I didn't say it clearly since I was in a hurry.

If we move memblock_add_node() forward before hotadd_new_pgdat(),
then node_start_pfn and node_end_pfn won't be 0. And
zone_spanned_pages_in_node() and zone_absent_pages_in_node() won't
return 0.

In your patch, they will return 0. And that leads to the print problem.

>
>> This is caused by a little bug in your patch 1.
>>
>> You should put memblock_add_node(start, size, nid) before hotadd_new_pgdat()
>> because:
>>
> My patch is just add an empty node first, later __add_zone() will update the size.
> But it is all right put here, and it can fix the print bug.

Yes. I just found this bug in the log.

>
>> hotadd_new_pgdat()
>>   | --> free_area_init_node()
>>            | --> get_pfn_range_for_nid()
>>                     | --> find memory ranges in memblock.
>>
>> | --> memblock_add_node(start, size, nid) -------------------    if you add it here, it doesn't work.
>>
>> The result will be like below if we hotadd node 5.
>> [ 2007.577000] Initmem setup node 5 [mem 0x0000000000000000-0xffffffffffffffff]
> 	pr_info("Initmem setup node %d [mem %#018Lx-%#018Lx]\n", nid,
> 		(u64)start_pfn << PAGE_SHIFT, ((u64)end_pfn << PAGE_SHIFT) - 1);
> start_pfn and end_pfn are both 0, and 0-1 -> 0xffffffffffffffff, right?

Yes.

>
>> [ 2007.584000] On node 5 totalpages: 0
>> [ 2007.585000] Built 5 zonelists in Node order, mobility grouping on.  Total pages: 32588823
>> [ 2007.594000] Policy zone: Normal
>> [ 2007.598000] init_memory_mapping: [mem 0x60000000000-0x607ffffffff]
>>
>>
>> And also, if we merge this patch, /sys/devices/system/node/nodeX/meminfo will break.
>>
> trigger call trace?

No. There is no error output. But if you see 
/sys/devices/system/node/nodeX/meminfo,
memory size will double because totalpages is calculated once here, and 
one more time
when onlining memory.

I think reset it to 0 in add_memory() is just a temporary solution. Will 
improve it in the
future.

Thanks.

>
>> Since this patch is not merged, I think let's just drop it.
>>
>> And about the little bug in your patch 1, since I'm in a hurry, I have already send a patch to fix it.
>>
>>
>> Thanks. :)
>>
>>
>> On 08/11/2015 03:33 PM, Xishi Qiu wrote:
>>> After hotadd_new_pgdat()->free_area_init_node(), the pgdat and zone's spanned/present
>>> are both 0, so remove reset_node_managed_pages() and reset_node_managed_pages().
>>>
>>> Signed-off-by: Xishi Qiu <qiuxishi@huawei.com>
>>> ---
>>>    mm/memory_hotplug.c | 25 -------------------------
>>>    1 file changed, 25 deletions(-)
>>>
>>> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
>>> index 11f26cc..997dfad 100644
>>> --- a/mm/memory_hotplug.c
>>> +++ b/mm/memory_hotplug.c
>>> @@ -1065,16 +1065,6 @@ int __ref online_pages(unsigned long pfn, unsigned long nr_pages, int online_typ
>>>    }
>>>    #endif /* CONFIG_MEMORY_HOTPLUG_SPARSE */
>>>    -static void reset_node_present_pages(pg_data_t *pgdat)
>>> -{
>>> -    struct zone *z;
>>> -
>>> -    for (z = pgdat->node_zones; z < pgdat->node_zones + MAX_NR_ZONES; z++)
>>> -        z->present_pages = 0;
>>> -
>>> -    pgdat->node_present_pages = 0;
>>> -}
>>> -
>>>    /* we are OK calling __meminit stuff here - we have CONFIG_MEMORY_HOTPLUG */
>>>    static pg_data_t __ref *hotadd_new_pgdat(int nid, u64 start)
>>>    {
>>> @@ -1109,21 +1099,6 @@ static pg_data_t __ref *hotadd_new_pgdat(int nid, u64 start)
>>>        build_all_zonelists(pgdat, NULL);
>>>        mutex_unlock(&zonelists_mutex);
>>>    -    /*
>>> -     * zone->managed_pages is set to an approximate value in
>>> -     * free_area_init_core(), which will cause
>>> -     * /sys/device/system/node/nodeX/meminfo has wrong data.
>>> -     * So reset it to 0 before any memory is onlined.
>>> -     */
>>> -    reset_node_managed_pages(pgdat);
>>> -
>>> -    /*
>>> -     * When memory is hot-added, all the memory is in offline state. So
>>> -     * clear all zones' present_pages because they will be updated in
>>> -     * online_pages() and offline_pages().
>>> -     */
>>> -    reset_node_present_pages(pgdat);
>>> -
>>>        return pgdat;
>>>    }
>>>    
>>
>> .
>>
>
>
> .
>

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#1212085

On 2015/8/24 17:39, Tang Chen wrote:

> 
> On 08/24/2015 05:17 PM, Xishi Qiu wrote:
>> On 2015/8/23 18:28, Tang Chen wrote:
>>
>>> Hi Shi,
>>>
>>> Sorry for the late reply. I hope it won't be too late.
>>>
>>> NON-ACK by me, I think.
>>>
>>> I noticed that your first has been merged. But it won't fix the problem
>>> these code intended to fix.
>>>
>>> After your patch 1, zone's spanned/present won't be set to 0 because:
>>>
>>> free_area_init_node()
>>>   |--> get_pfn_range_for_nid(&start_pfn, &end_pfn)
>>>   |--> calculate_node_totalpages(pgdat, start_pfn, end_pfn, ...)
>>>           | --> zone_spanned_pages_in_node()
>>>                    | --> if (!node_start_pfn && !node_end_pfn) return 0;    --------    false, won't return 0
>>>           | --> zone_absent_pages_in_node()
>>>                    | --> if (!node_start_pfn && !node_end_pfn) return 0;    --------    false, won't return 0
>>>
>> Hi Tang,
>>
>> Thank you for your reply. When we add a new node, it is not included in the
>> memblock, I have no idea why zone_spanned_pages_in_node() and zone_absent_pages_in_node()
>> won't return 0. Do you add some debug code and print it?
> 
> Sorry, I didn't say it clearly since I was in a hurry.
> 
> If we move memblock_add_node() forward before hotadd_new_pgdat(),
> then node_start_pfn and node_end_pfn won't be 0. And
> zone_spanned_pages_in_node() and zone_absent_pages_in_node() won't
> return 0.
> 
> In your patch, they will return 0. And that leads to the print problem.
> 
>>
>>> This is caused by a little bug in your patch 1.
>>>
>>> You should put memblock_add_node(start, size, nid) before hotadd_new_pgdat()
>>> because:
>>>
>> My patch is just add an empty node first, later __add_zone() will update the size.
>> But it is all right put here, and it can fix the print bug.
> 
> Yes. I just found this bug in the log.
> 
>>
>>> hotadd_new_pgdat()
>>>   | --> free_area_init_node()
>>>            | --> get_pfn_range_for_nid()
>>>                     | --> find memory ranges in memblock.
>>>
>>> | --> memblock_add_node(start, size, nid) -------------------    if you add it here, it doesn't work.
>>>
>>> The result will be like below if we hotadd node 5.
>>> [ 2007.577000] Initmem setup node 5 [mem 0x0000000000000000-0xffffffffffffffff]
>>     pr_info("Initmem setup node %d [mem %#018Lx-%#018Lx]\n", nid,
>>         (u64)start_pfn << PAGE_SHIFT, ((u64)end_pfn << PAGE_SHIFT) - 1);
>> start_pfn and end_pfn are both 0, and 0-1 -> 0xffffffffffffffff, right?
> 
> Yes.
> 
>>
>>> [ 2007.584000] On node 5 totalpages: 0
>>> [ 2007.585000] Built 5 zonelists in Node order, mobility grouping on.  Total pages: 32588823
>>> [ 2007.594000] Policy zone: Normal
>>> [ 2007.598000] init_memory_mapping: [mem 0x60000000000-0x607ffffffff]
>>>
>>>
>>> And also, if we merge this patch, /sys/devices/system/node/nodeX/meminfo will break.
>>>
>> trigger call trace?
> 
> No. There is no error output. But if you see /sys/devices/system/node/nodeX/meminfo,
> memory size will double because totalpages is calculated once here, and one more time
> when onlining memory.
> 

Hi Tang,

Do you mean si_meminfo_node() -> val->totalram = managed_pages; will be added double?
But my patch will keep it 0 in hotadd_new_pgdat(), so it will not be double, right?

Thanks,
Xishi Qiu

> I think reset it to 0 in add_memory() is just a temporary solution. Will improve it in the
> future.
> 
> Thanks.
> 
>>
>>> Since this patch is not merged, I think let's just drop it.
>>>
>>> And about the little bug in your patch 1, since I'm in a hurry, I have already send a patch to fix it.
>>>
>>>
>>> Thanks. :)
>>>
>>>
>>> On 08/11/2015 03:33 PM, Xishi Qiu wrote:
>>>> After hotadd_new_pgdat()->free_area_init_node(), the pgdat and zone's spanned/present
>>>> are both 0, so remove reset_node_managed_pages() and reset_node_managed_pages().
>>>>
>>>> Signed-off-by: Xishi Qiu <qiuxishi@huawei.com>
>>>> ---
>>>>    mm/memory_hotplug.c | 25 -------------------------
>>>>    1 file changed, 25 deletions(-)
>>>>
>>>> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
>>>> index 11f26cc..997dfad 100644
>>>> --- a/mm/memory_hotplug.c
>>>> +++ b/mm/memory_hotplug.c
>>>> @@ -1065,16 +1065,6 @@ int __ref online_pages(unsigned long pfn, unsigned long nr_pages, int online_typ
>>>>    }
>>>>    #endif /* CONFIG_MEMORY_HOTPLUG_SPARSE */
>>>>    -static void reset_node_present_pages(pg_data_t *pgdat)
>>>> -{
>>>> -    struct zone *z;
>>>> -
>>>> -    for (z = pgdat->node_zones; z < pgdat->node_zones + MAX_NR_ZONES; z++)
>>>> -        z->present_pages = 0;
>>>> -
>>>> -    pgdat->node_present_pages = 0;
>>>> -}
>>>> -
>>>>    /* we are OK calling __meminit stuff here - we have CONFIG_MEMORY_HOTPLUG */
>>>>    static pg_data_t __ref *hotadd_new_pgdat(int nid, u64 start)
>>>>    {
>>>> @@ -1109,21 +1099,6 @@ static pg_data_t __ref *hotadd_new_pgdat(int nid, u64 start)
>>>>        build_all_zonelists(pgdat, NULL);
>>>>        mutex_unlock(&zonelists_mutex);
>>>>    -    /*
>>>> -     * zone->managed_pages is set to an approximate value in
>>>> -     * free_area_init_core(), which will cause
>>>> -     * /sys/device/system/node/nodeX/meminfo has wrong data.
>>>> -     * So reset it to 0 before any memory is onlined.
>>>> -     */
>>>> -    reset_node_managed_pages(pgdat);
>>>> -
>>>> -    /*
>>>> -     * When memory is hot-added, all the memory is in offline state. So
>>>> -     * clear all zones' present_pages because they will be updated in
>>>> -     * online_pages() and offline_pages().
>>>> -     */
>>>> -    reset_node_present_pages(pgdat);
>>>> -
>>>>        return pgdat;
>>>>    }
>>>>    
>>>
>>> .
>>>
>>
>>
>> .
>>
> 
> 
> .
> 



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#1213607

On 08/24/2015 07:24 PM, Xishi Qiu wrote:
> ......
>>>> [ 2007.584000] On node 5 totalpages: 0
>>>> [ 2007.585000] Built 5 zonelists in Node order, mobility grouping on.  Total pages: 32588823
>>>> [ 2007.594000] Policy zone: Normal
>>>> [ 2007.598000] init_memory_mapping: [mem 0x60000000000-0x607ffffffff]
>>>>
>>>>
>>>> And also, if we merge this patch, /sys/devices/system/node/nodeX/meminfo will break.
>>>>
>>> trigger call trace?
>> No. There is no error output. But if you see /sys/devices/system/node/nodeX/meminfo,
>> memory size will double because totalpages is calculated once here, and one more time
>> when onlining memory.
>>
> Hi Tang,
>
> Do you mean si_meminfo_node() -> val->totalram = managed_pages; will be added double?
> But my patch will keep it 0 in hotadd_new_pgdat(), so it will not be double, right?
>

Hi,

I mean this:

online_pages()
|--> zone->zone_pgdat->node_present_pages += onlined_pages;

It will be double.

Since meminfo data is retrieved from these kernel structures, /proc/meminfo
will be broken.


Actually speaking, reset it when hot-adding memory is not a good idea.
We should make the memory init code be suitable for both boot code and
memory hot-plug code.


Thanks.
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