Messages in this thread | | | From | Huaisheng Ye <> | Subject | [RFC PATCH v2 00/12] get rid of GFP_ZONE_TABLE/BAD | Date | Mon, 21 May 2018 23:20:21 +0800 |
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From: Huaisheng Ye <yehs1@lenovo.com>
Replace GFP_ZONE_TABLE and GFP_ZONE_BAD with encoded zone number.
Delete ___GFP_DMA, ___GFP_HIGHMEM and ___GFP_DMA32 from GFP bitmasks, the bottom three bits of GFP mask is reserved for storing encoded zone number.
The encoding method is XOR. Get zone number from enum zone_type, then encode the number with ZONE_NORMAL by XOR operation. The goal is to make sure ZONE_NORMAL can be encoded to zero. So, the compatibility can be guaranteed, such as GFP_KERNEL and GFP_ATOMIC can be used as before.
Reserve __GFP_MOVABLE in bit 3, so that it can continue to be used as a flag. Same as before, __GFP_MOVABLE respresents movable migrate type for ZONE_DMA, ZONE_DMA32, and ZONE_NORMAL. But when it is enabled with __GFP_HIGHMEM, ZONE_MOVABLE shall be returned instead of ZONE_HIGHMEM. __GFP_ZONE_MOVABLE is created to realize it.
With this patch, just enabling __GFP_MOVABLE and __GFP_HIGHMEM is not enough to get ZONE_MOVABLE from gfp_zone. All callers should use GFP_HIGHUSER_MOVABLE or __GFP_ZONE_MOVABLE directly to achieve that.
Decode zone number directly from bottom three bits of flags in gfp_zone. The theory of encoding and decoding is, A ^ B ^ B = A
Changes since v1,
v2: Add __GFP_ZONE_MOVABLE and modify GFP_HIGHUSER_MOVABLE to help callers to get ZONE_MOVABLE. Add __GFP_ZONE_MASK to mask lowest 3 bits of GFP bitmasks. Modify some callers' gfp flag to update usage of address zone modifiers. Modify inline function gfp_zone to get better performance according to Matthew's suggestion.
Link: https://marc.info/?l=linux-mm&m=152596791931266&w=2
Huaisheng Ye (12): include/linux/gfp.h: get rid of GFP_ZONE_TABLE/BAD arch/x86/kernel/amd_gart_64: update usage of address zone modifiers arch/x86/kernel/pci-calgary_64: update usage of address zone modifiers drivers/iommu/amd_iommu: update usage of address zone modifiers include/linux/dma-mapping: update usage of address zone modifiers drivers/xen/swiotlb-xen: update usage of address zone modifiers fs/btrfs/extent_io: update usage of address zone modifiers drivers/block/zram/zram_drv: update usage of address zone modifiers mm/vmpressure: update usage of address zone modifiers mm/zsmalloc: update usage of address zone modifiers include/linux/highmem: update usage of movableflags arch/x86/include/asm/page.h: update usage of movableflags
arch/x86/include/asm/page.h | 3 +- arch/x86/kernel/amd_gart_64.c | 2 +- arch/x86/kernel/pci-calgary_64.c | 2 +- drivers/block/zram/zram_drv.c | 6 +-- drivers/iommu/amd_iommu.c | 2 +- drivers/xen/swiotlb-xen.c | 2 +- fs/btrfs/extent_io.c | 2 +- include/linux/dma-mapping.h | 2 +- include/linux/gfp.h | 98 +++++----------------------------------- include/linux/highmem.h | 4 +- mm/vmpressure.c | 2 +- mm/zsmalloc.c | 4 +- 12 files changed, 26 insertions(+), 103 deletions(-)
-- 1.8.3.1
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