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Date: Mon, 24 Aug 2015 19:24:27 +0800
From: Xishi Qiu <qiuxishi@...wei.com>
To: Tang Chen <tangchen@...fujitsu.com>
CC: Andrew Morton <akpm@...ux-foundation.org>,
Yasuaki Ishimatsu <isimatu.yasuaki@...fujitsu.com>,
Kamezawa Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
<izumi.taku@...fujitsu.com>, Linux MM <linux-mm@...ck.org>,
LKML <linux-kernel@...r.kernel.org>,
Yasuaki Ishimatsu <yasu.isimatu@...il.com>
Subject: Re: [PATCH 2/2] memory-hotplug: remove reset_node_managed_pages()
and reset_node_managed_pages() in hotadd_new_pgdat()
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@...wei.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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