On 11/5/18 3:50 AM, Huang, Ying wrote:
> Vasily Averin <vvs@xxxxxxxxxxxxx> writes:
>
>> commit a2468cc9bfdf ("swap: choose swap device according to numa node")
>> increased size of swap_info_struct up to 44 Kbytes, now it requires
>> 4th order page.
>
> Why swap_info_struct could be so large? Because MAX_NUMNODES could be
> thousands so that 'avail_lists' field could be tens KB? If so, I think
> it's fair to use kvzalloc(). Can you add one line comment? Because
> struct swap_info_struct is quite small in default configuration.
I was incorrect not 44Kb but 40kb should be here.
We have found CONFIG_NODES_SHIFT=10 in new RHEL7 update 6 kernel,
default ubuntu kernels have the same setting too.
crash> struct swap_info_struct -o
struct swap_info_struct {
[0] unsigned long flags;
[8] short prio;
...
[140] spinlock_t lock;
[144] struct plist_node list;
[184] struct plist_node avail_lists[1024]; <<<< here
[41144] struct swap_cluster_info *cluster_info;
[41152] struct swap_cluster_list free_clusters;
...
[41224] spinlock_t cont_lock;
}
SIZE: 41232
struct swap_info_struct {
...
RH_KABI_EXTEND(struct plist_node avail_lists[MAX_NUMNODES]) /* entry in swap_avail_head */
...
}
#define MAX_NUMNODES (1 << NODES_SHIFT)
#ifdef CONFIG_NODES_SHIFT
#define NODES_SHIFT CONFIG_NODES_SHIFT
#else
#define NODES_SHIFT 0
#endif
/boot/config-4.15.0-38-generic:CONFIG_NODES_SHIFT=10
