On Tue, Mar 07, 2017 at 10:28:41AM -0800, Matthew Wilcox wrote: > On Tue, Mar 07, 2017 at 03:10:20PM +0100, Michal Hocko wrote: > > This patch simply uses __GFP_HIGHMEM implicitly when allocating pages to > > be mapped to the vmalloc space. Current users which add __GFP_HIGHMEM > > are simplified and drop the flag.
btw, I had another idea for GFP_HIGHMEM -- remove it when CONFIG_HIGHMEM isn't enabled. Saves 26 bytes of .text and 64 bytes of .data on my laptop's kernel build. What do you think? Also, I suspect the layout of bits is suboptimal from an assembly language perspective. I still mostly care about x86 which doesn't benefit, so I'm not inclined to do the work, but certainly ARM, PA-RISC, SPARC and Itanium would all benefit from having frequently-used bits (ie those used in GFP_KERNEL and GFP_ATOMIC) placed in the low 8 bits. diff --git a/include/linux/gfp.h b/include/linux/gfp.h index 0fe0b6295ab5..d88cb532d7c8 100644 --- a/include/linux/gfp.h +++ b/include/linux/gfp.h @@ -16,7 +16,11 @@ struct vm_area_struct; /* Plain integer GFP bitmasks. Do not use this directly. */ #define ___GFP_DMA 0x01u +#ifdef CONFIG_HIGHMEM #define ___GFP_HIGHMEM 0x02u +#else +#define ___GFP_HIGHMEM 0x0u +#endif #define ___GFP_DMA32 0x04u #define ___GFP_MOVABLE 0x08u #define ___GFP_RECLAIMABLE 0x10u
