From 8b368e8e961944105945fbe36f3f264252bfd19a Mon Sep 17 00:00:00 2001 From: Dan Williams Date: Thu, 25 Feb 2016 01:02:30 +0000 Subject: [PATCH] mm: CONFIG_NR_ZONES_EXTENDED ZONE_DEVICE (merged in 4.3) and ZONE_CMA (proposed) are examples of new mm zones that are bumping up against the current maximum limit of 4 zones, i.e. 2 bits in page->flags. When adding a zone this equation still needs to be satisified: SECTIONS_WIDTH + ZONES_WIDTH + NODES_SHIFT + LAST_CPUPID_SHIFT <= BITS_PER_LONG - NR_PAGEFLAGS ZONE_DEVICE currently tries to satisfy this equation by requiring that ZONE_DMA be disabled, but this is untenable given generic kernels want to support ZONE_DEVICE and ZONE_DMA simultaneously. ZONE_CMA would like to increase the amount of memory covered per section, but that limits the minimum granularity at which consecutive memory ranges can be added via devm_memremap_pages(). The trade-off of what is acceptable to sacrifice depends heavily on the platform. For example, ZONE_CMA is targeted for 32-bit platforms where page->flags is constrained, but those platforms likely do not care about the minimum granularity of memory hotplug. A big iron machine with 1024 numa nodes can likely sacrifice ZONE_DMA where a general purpose distribution kernel can not. CONFIG_NR_ZONES_EXTENDED is a configuration symbol that gets selected when the number of configured zones exceeds 4. It documents the configuration symbols and definitions that get modified when ZONES_WIDTH is greater than 2. For now, it steals a bit from NODES_SHIFT. Later on it can be used to document the definitions that get modified when a 32-bit configuration wants more zone bits. Note that GFP_ZONE_TABLE poses an interesting constraint since include/linux/gfp.h gets included by the 32-bit portion of a 64-bit build. We need to be careful to only build the table for zones that have a corresponding gfp_t flag. GFP_ZONES_SHIFT is introduced for this purpose. This patch does not attempt to solve the problem of adding a new zone that also has a corresponding GFP_ flag. Link: https://bugzilla.kernel.org/show_bug.cgi?id=110931 Fixes: 033fbae988fc ("mm: ZONE_DEVICE for "device memory"") Signed-off-by: Dan Williams Reported-by: Mark Cc: Mel Gorman Cc: Rik van Riel Cc: Joonsoo Kim Cc: Dave Hansen Cc: Sudip Mukherjee Signed-off-by: Andrew Morton --- arch/x86/Kconfig | 6 ++++-- include/linux/gfp.h | 33 ++++++++++++++++++++------------- include/linux/page-flags-layout.h | 2 ++ mm/Kconfig | 7 +++++-- 4 files changed, 31 insertions(+), 17 deletions(-) diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig index 3fef519..b94704a 100644 --- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -1409,8 +1409,10 @@ config NUMA_EMU config NODES_SHIFT int "Maximum NUMA Nodes (as a power of 2)" if !MAXSMP - range 1 10 - default "10" if MAXSMP + range 1 10 if !NR_ZONES_EXTENDED + range 1 9 if NR_ZONES_EXTENDED + default "10" if MAXSMP && !NR_ZONES_EXTENDED + default "9" if MAXSMP && NR_ZONES_EXTENDED default "6" if X86_64 default "3" depends on NEED_MULTIPLE_NODES diff --git a/include/linux/gfp.h b/include/linux/gfp.h index af1f2b2..d201d8a 100644 --- a/include/linux/gfp.h +++ b/include/linux/gfp.h @@ -329,22 +329,29 @@ static inline bool gfpflags_allow_blocking(const gfp_t gfp_flags) * 0xe => BAD (MOVABLE+DMA32+HIGHMEM) * 0xf => BAD (MOVABLE+DMA32+HIGHMEM+DMA) * - * ZONES_SHIFT must be <= 2 on 32 bit platforms. + * GFP_ZONES_SHIFT must be <= 2 on 32 bit platforms. */ -#if 16 * ZONES_SHIFT > BITS_PER_LONG -#error ZONES_SHIFT too large to create GFP_ZONE_TABLE integer +#if defined(CONFIG_ZONE_DEVICE) && (MAX_NR_ZONES-1) <= 4 +/* ZONE_DEVICE is not a valid GFP zone specifier */ +#define GFP_ZONES_SHIFT 2 +#else +#define GFP_ZONES_SHIFT ZONES_SHIFT +#endif + +#if 16 * GFP_ZONES_SHIFT > BITS_PER_LONG +#error GFP_ZONES_SHIFT too large to create GFP_ZONE_TABLE integer #endif #define GFP_ZONE_TABLE ( \ - (ZONE_NORMAL << 0 * ZONES_SHIFT) \ - | (OPT_ZONE_DMA << ___GFP_DMA * ZONES_SHIFT) \ - | (OPT_ZONE_HIGHMEM << ___GFP_HIGHMEM * ZONES_SHIFT) \ - | (OPT_ZONE_DMA32 << ___GFP_DMA32 * ZONES_SHIFT) \ - | (ZONE_NORMAL << ___GFP_MOVABLE * ZONES_SHIFT) \ - | (OPT_ZONE_DMA << (___GFP_MOVABLE | ___GFP_DMA) * ZONES_SHIFT) \ - | (ZONE_MOVABLE << (___GFP_MOVABLE | ___GFP_HIGHMEM) * ZONES_SHIFT) \ - | (OPT_ZONE_DMA32 << (___GFP_MOVABLE | ___GFP_DMA32) * ZONES_SHIFT) \ + (ZONE_NORMAL << 0 * GFP_ZONES_SHIFT) \ + | (OPT_ZONE_DMA << ___GFP_DMA * GFP_ZONES_SHIFT) \ + | (OPT_ZONE_HIGHMEM << ___GFP_HIGHMEM * GFP_ZONES_SHIFT) \ + | (OPT_ZONE_DMA32 << ___GFP_DMA32 * GFP_ZONES_SHIFT) \ + | (ZONE_NORMAL << ___GFP_MOVABLE * GFP_ZONES_SHIFT) \ + | (OPT_ZONE_DMA << (___GFP_MOVABLE | ___GFP_DMA) * GFP_ZONES_SHIFT) \ + | (ZONE_MOVABLE << (___GFP_MOVABLE | ___GFP_HIGHMEM) * GFP_ZONES_SHIFT) \ + | (OPT_ZONE_DMA32 << (___GFP_MOVABLE | ___GFP_DMA32) * GFP_ZONES_SHIFT) \ ) /* @@ -369,8 +376,8 @@ static inline enum zone_type gfp_zone(gfp_t flags) enum zone_type z; int bit = (__force int) (flags & GFP_ZONEMASK); - z = (GFP_ZONE_TABLE >> (bit * ZONES_SHIFT)) & - ((1 << ZONES_SHIFT) - 1); + z = (GFP_ZONE_TABLE >> (bit * GFP_ZONES_SHIFT)) & + ((1 << GFP_ZONES_SHIFT) - 1); VM_BUG_ON((GFP_ZONE_BAD >> bit) & 1); return z; } diff --git a/include/linux/page-flags-layout.h b/include/linux/page-flags-layout.h index da52366..77b078c 100644 --- a/include/linux/page-flags-layout.h +++ b/include/linux/page-flags-layout.h @@ -17,6 +17,8 @@ #define ZONES_SHIFT 1 #elif MAX_NR_ZONES <= 4 #define ZONES_SHIFT 2 +#elif MAX_NR_ZONES <= 8 +#define ZONES_SHIFT 3 #else #error ZONES_SHIFT -- too many zones configured adjust calculation #endif diff --git a/mm/Kconfig b/mm/Kconfig index 031a329..7826216 100644 --- a/mm/Kconfig +++ b/mm/Kconfig @@ -652,8 +652,6 @@ config IDLE_PAGE_TRACKING config ZONE_DEVICE bool "Device memory (pmem, etc...) hotplug support" - default !ZONE_DMA - depends on !ZONE_DMA depends on MEMORY_HOTPLUG depends on MEMORY_HOTREMOVE depends on X86_64 #arch_add_memory() comprehends device memory @@ -667,5 +665,10 @@ config ZONE_DEVICE If FS_DAX is enabled, then say Y. +config NR_ZONES_EXTENDED + bool + default n if !64BIT + default y if ZONE_DEVICE && ZONE_DMA && ZONE_DMA32 + config FRAME_VECTOR bool -- 2.5.0