[PATCH] mm/vmscan : use vmcan_swappiness( ) basing on MEMCG config to elimiate unnecessary runtime cost

Currently, we get the vm_swappiness via vmscan_swappiness(), which calls global_reclaim() to check if this is a global reclaim. Besides, the current implementation of global_reclaim() always returns true for the !CONFIG_MEGCG case, and judges the other case by checking whether

[PATCH] mm/vmscan : use vmcan_swappiness( ) basing on MEMCG config to elimiate unnecessary runtime cost

Currently, we get the vm_swappiness via vmscan_swappiness(), which calls global_reclaim() to check if this is a global reclaim. Besides, the current implementation of global_reclaim() always returns true for the !CONFIG_MEGCG case, and judges the other case by checking whether