Mastering Linux Kernel Development

Page reclaim modifiers

As systems load increases, the amount of free memory in zones might fall below the low watermark, resulting in memory crunch that will acutely impact overall performance of the system. To handle such eventuality, the memory manager is equipped with page reclaim algorithms, which are implemented to identify and reclaim pages. Kernel memory allocator routines, engage reclaim algorithms when invoked with appropriate GFP constants called page reclaim modifiers:

#define __GFP_IO ((__force gfp_t)___GFP_IO)#define __GFP_FS ((__force gfp_t)___GFP_FS)#define __GFP_DIRECT_RECLAIM ((__force gfp_t)___GFP_DIRECT_RECLAIM) /* Caller can reclaim */#define __GFP_KSWAPD_RECLAIM ((__force gfp_t)___GFP_KSWAPD_RECLAIM) /* kswapd can wake ...