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

From: Anshuman Khandual <[email-masked]>
Date: Thu, 03 Mar 2016 15:11:08 +0530

On 03/03/2016 12:31 PM, Li Zhang wrote:
> From: Li Zhang <[email-masked]>
> 
> 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

Typo here ....................................^^^^^^^^

> fixed with a completion to wait for all memory initialised in
> page_alloc_init_late(). It is to fix the oom problem on X86

You can just write *out of memory* instead of *oom* or put them in
capitals.

> 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

I am wondering how its going to impact other architectures.

> 
> 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:

The dmesg output here needs some formatting.

> 
> Signed-off-by: Li Zhang <[email-masked]>
> ---
>  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) &&

Does this change need to be tested on all architectures ?