Messages in this thread | | | Subject | Re: [PATCH 1/2] mm: use kvzalloc for swap_info_struct allocation | From | Vasily Averin <> | Date | Mon, 5 Nov 2018 07:59:13 +0300 |
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On 11/5/18 3:50 AM, Huang, Ying wrote: > Vasily Averin <vvs@virtuozzo.com> 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
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