Subject: Re: [PATCH] ovs: do not allocate memory from offline numa node

From: Vlastimil Babka <[email-masked]>
Date: Mon, 5 Oct 2015 15:59:20 +0200

On 10/02/2015 12:18 PM, Konstantin Khlebnikov wrote:
> When openvswitch tries allocate memory from offline numa node 0:
> stats = kmem_cache_alloc_node(flow_stats_cache, GFP_KERNEL | __GFP_ZERO, 0)
> It catches VM_BUG_ON(nid < 0 || nid >= MAX_NUMNODES || !node_online(nid))
> [ replaced with VM_WARN_ON(!node_online(nid)) recently ] in linux/gfp.h
> This patch disables numa affinity in this case.
>
> Signed-off-by: Konstantin Khlebnikov <[email-masked]>

...

> diff --git a/net/openvswitch/flow_table.c b/net/openvswitch/flow_table.c
> index f2ea83ba4763..c7f74aab34b9 100644
> --- a/net/openvswitch/flow_table.c
> +++ b/net/openvswitch/flow_table.c
> @@ -93,7 +93,8 @@ struct sw_flow *ovs_flow_alloc(void)
>
>   	/* Initialize the default stat node. */
>   	stats = kmem_cache_alloc_node(flow_stats_cache,
> -				      GFP_KERNEL | __GFP_ZERO, 0);
> +				      GFP_KERNEL | __GFP_ZERO,
> +				      node_online(0) ? 0 : NUMA_NO_NODE);

Stupid question: can node 0 become offline between this check, and the 
VM_WARN_ON? :) BTW what kind of system has node 0 offline?

>   	if (!stats)
>   		goto err;