[PATCH RFC 1/2] mm: meminit: initialise more memory for inode/dentry hash tables in early boot

[Li Zhang]

From: Li Zhang <zhlcindy@xxxxxxxxxxxxxxxxxx>

This patch is based on Mel Gorman's old patch in the mailing list,
https://lkml.org/lkml/2015/5/5/280 which is dicussed but it is
fixed with a completion to wait for all memory initialised in
page_alloc_init_late(). It is to fix the oom problem on X86
with 24TB memory which allocates memory in late initialisation.
But for Power platform with 32TB memory, it causes a call trace
in vfs_caches_init->inode_init() and inode hash table needs more
memory.
So this patch allocates 1GB for 0.25TB/node for large system
as it is mentioned in https://lkml.org/lkml/2015/5/1/627

This call trace is found on Power with 32TB memory, 1024CPUs, 16nodes.
The log from dmesg as the following:

[    0.091780] Dentry cache hash table entries: 2147483648 (order: 18,
17179869184 bytes)
[    2.891012] vmalloc: allocation failure, allocated 16021913600 of
17179934720 bytes
[    2.891034] swapper/0: page allocation failure: order:0,
mode:0x2080020
[    2.891038] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 4.4.0-0-ppc64
[    2.891041] Call Trace:
[    2.891046] [c0000000012bfa00] [c0000000007c4a50]
                .dump_stack+0xb4/0xb664 (unreliable)
[    2.891051] [c0000000012bfa80] [c0000000001f93d4]
                .warn_alloc_failed+0x114/0x160
[    2.891054] [c0000000012bfb30] [c00000000023c204]
                .__vmalloc_area_node+0x1a4/0x2b0
[    2.891058] [c0000000012bfbf0] [c00000000023c3f4]
                .__vmalloc_node_range+0xe4/0x110
[    2.891061] [c0000000012bfc90] [c00000000023c460]
                .__vmalloc_node+0x40/0x50
[    2.891065] [c0000000012bfd10] [c000000000b67d60]
                .alloc_large_system_hash+0x134/0x2a4
[    2.891068] [c0000000012bfdd0] [c000000000b70924]
                .inode_init+0xa4/0xf0
[    2.891071] [c0000000012bfe60] [c000000000b706a0]
                .vfs_caches_init+0x80/0x144
[    2.891074] [c0000000012bfef0] [c000000000b35208]
                .start_kernel+0x40c/0x4e0
[    2.891078] [c0000000012bff90] [c000000000008cfc]
                start_here_common+0x20/0x4a4
[    2.891080] Mem-Info:

Signed-off-by: Li Zhang <zhlcindy@xxxxxxxxxxxxxxxxxx>
---
 mm/page_alloc.c | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 838ca8bb..4847f25 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -293,13 +293,20 @@ static inline bool update_defer_init(pg_data_t *pgdat,
 				unsigned long pfn, unsigned long zone_end,
 				unsigned long *nr_initialised)
 {
+	unsigned long max_initialise;
+
 	/* Always populate low zones for address-contrained allocations */
 	if (zone_end < pgdat_end_pfn(pgdat))
 		return true;
+	/*
+	* Initialise at least 2G of a node but also take into account that
+	* two large system hashes that can take up 1GB for 0.25TB/node.
+	*/
+	max_initialise = max(2UL << (30 - PAGE_SHIFT),
+		(pgdat->node_spanned_pages >> 8));
 
-	/* Initialise at least 2G of the highest zone */
 	(*nr_initialised)++;
-	if (*nr_initialised > (2UL << (30 - PAGE_SHIFT)) &&
+	if ((*nr_initialised > max_initialise) &&
 	    (pfn & (PAGES_PER_SECTION - 1)) == 0) {
 		pgdat->first_deferred_pfn = pfn;
 		return false;
-- 
2.1.0