From 673e9ab6b64f981159aeff3b65675bb7dbedecd8 Mon Sep 17 00:00:00 2001 From: Sudarshan Rajagopalan Date: Fri, 8 Jan 2021 15:16:00 -0800 Subject: [PATCH] FROMLIST: arm64: reduce section size for sparsemem Reducing the section size helps reduce wastage of reserved memory for huge memory holes in sparsemem model. But having a much smaller section size bits could break PMD mappings for vmemmap and wouldn't accomodate the highest order page for certain page size granule configs. It is determined that SECTION_SIZE_BITS of 27 (128MB) could be ideal default value for 4K_PAGES that gives least section size without breaking PMD based vmemmap mappings. For simplicity, 16K_PAGES could follow the same as 4K_PAGES. And the least SECTION_SIZE_BITS for 64K_PAGES is 29 that could accomodate MAX_ORDER. Signed-off-by: Sudarshan Rajagopalan Suggested-by: David Hildenbrand Cc: Will Deacon Cc: Anshuman Khandual Cc: Mike Rapoport Cc: Mark Rutland Cc: Suren Baghdasaryan Link: https://lore.kernel.org/lkml/15cf9a2359197fee0168f820c5c904650d07939e.1610146597.git.sudaraja@codeaurora.org/ Bug: 175715646 Signed-off-by: Suren Baghdasaryan Change-Id: Iecc0369c595bcabe01182a85a5464c87df36c217 --- arch/arm64/include/asm/sparsemem.h | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-) diff --git a/arch/arm64/include/asm/sparsemem.h b/arch/arm64/include/asm/sparsemem.h index 1f43fcc79738..ff08ff6b677c 100644 --- a/arch/arm64/include/asm/sparsemem.h +++ b/arch/arm64/include/asm/sparsemem.h @@ -7,7 +7,13 @@ #ifdef CONFIG_SPARSEMEM #define MAX_PHYSMEM_BITS CONFIG_ARM64_PA_BITS -#define SECTION_SIZE_BITS 30 -#endif + +#if defined(CONFIG_ARM64_4K_PAGES) || defined(CONFIG_ARM64_16K_PAGES) +#define SECTION_SIZE_BITS 27 +#else +#define SECTION_SIZE_BITS 29 +#endif /* CONFIG_ARM64_4K_PAGES || CONFIG_ARM64_16K_PAGES */ + +#endif /* CONFIG_SPARSEMEM*/ #endif