vm_compressor_mode (vm.compressor_mode) values for enabled compressed memory in OS X

## Background In Super user, with an accepted answer : - **Disable** compressed memory in Mac OS 10.9 Mavericks? Also in Super User: - how to get memory compress back in Mac OS 10.9 Mavericks? – and from the first answer there we understand that the value of *boot argument* vm_compressor does not correspond with the value of *sysctl variable* vm.compressor_mode. In Apple open source for OS X 10.9, Mavericks; in xnu-2422.1.72: - vm_compressor.c - vm_fault.c - vm_pageout.h In vm_compressor.c: /* * vm_compressor_mode has a heirarchy of control to set its value. * boot-args are checked first, then device-tree, and finally * the default value that is defined below. See vm_fault_init() for * the boot-arg & device-tree code. */ On a MacBookPro5,2 with 8 GB memory I find: sh-3.2$ sysctl -a vm.compressor_mode vm.compressor_mode: 4 Near the foot of vm_pageout.h: extern int vm_compressor_mode; extern int vm_compressor_thread_count; #define VM_PAGER_DEFAULT 0x1 /* Use default pager. */ #define VM_PAGER_COMPRESSOR_NO_SWAP 0x2 /* In-core compressor only. */ #define VM_PAGER_COMPRESSOR_WITH_SWAP 0x4 /* In-core compressor + swap backend. */ #define VM_PAGER_FREEZER_DEFAULT 0x8 /* Freezer backed by default pager.*/ #define VM_PAGER_FREEZER_COMPRESSOR_NO_SWAP 0x10 /* Freezer backed by in-core compressor only i.e. frozen data remain in-core compressed.*/ #define VM_PAGER_FREEZER_COMPRESSOR_WITH_SWAP 0x20 /* Freezer backed by in-core compressor with swap support too.*/ #define VM_PAGER_MAX_MODES 6 /* Total number of vm compressor modes supported */ #define DEFAULT_PAGER_IS_ACTIVE ((vm_compressor_mode & VM_PAGER_DEFAULT) == VM_PAGER_DEFAULT) #define COMPRESSED_PAGER_IS_ACTIVE (vm_compressor_mode & (VM_PAGER_COMPRESSOR_NO_SWAP | VM_PAGER_COMPRESSOR_WITH_SWAP)) #define DEFAULT_FREEZER_IS_ACTIVE ((vm_compressor_mode & VM_PAGER_FREEZER_DEFAULT) == VM_PAGER_FREEZER_DEFAULT) #define DEFAULT_FREEZER_COMPRESSED_PAGER_IS_ACTIVE (vm_compressor_mode & (VM_PAGER_FREEZER_COMPRESSOR_NO_SWAP | VM_PAGER_FREEZER_COMPRESSOR_WITH_SWAP)) # Question Is it possible to have an **enabled** mode other than 4 for compressed memory ? If so, can we find a plain english explanation of the modes?