Re: [PATCH 2/2] memory-hotplug: remove reset_node_managed_pages() and reset_node_managed_pages() in hotadd_new_pgdat()
From: Tang Chen
Date: Mon Aug 24 2015 - 05:41:33 EST
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@xxxxxxxxxx>
---
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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