From 050b2da268f8fc4f8123f6462c430a61547b2f7b Mon Sep 17 00:00:00 2001 From: Mike Rapoport Date: Mon, 14 Dec 2020 19:10:04 -0800 Subject: arc: use FLATMEM with freeing of unused memory map instead of DISCONTIGMEM Currently ARC uses DISCONTIGMEM to cope with sparse physical memory address space on systems with 2 memory banks. While DISCONTIGMEM avoids wasting memory on unpopulated memory map, it adds both memory and CPU overhead relatively to FLATMEM. Moreover, DISCONTINGMEM is generally considered deprecated. The obvious replacement for DISCONTIGMEM would be SPARSEMEM, but it is also less efficient than FLATMEM in pfn_to_page() and page_to_pfn() conversions. Besides it requires tuning of SECTION_SIZE which is not trivial for possible ARC memory configuration. Since the memory map for both banks is always allocated from the "lowmem" bank, it is possible to use FLATMEM for two-bank configuration and simply free the unused hole in the memory map. All is required for that is to provide ARC-specific pfn_valid() that will take into account actual physical memory configuration and define HAVE_ARCH_PFN_VALID. The resulting kernel image configured with defconfig + HIGHMEM=y is smaller: $ size a/vmlinux b/vmlinux text data bss dec hex filename 4673503 1245456 279756 6198715 5e95bb a/vmlinux 4658706 1246864 279756 6185326 5e616e b/vmlinux $ ./scripts/bloat-o-meter a/vmlinux b/vmlinux add/remove: 28/30 grow/shrink: 42/399 up/down: 10986/-29025 (-18039) ... Total: Before=4709315, After = 4691276, chg -0.38% Booting nSIM with haps_ns.dts results in the following memory usage reports: a: Memory: 1559104K/1572864K available (3531K kernel code, 595K rwdata, 752K rodata, 136K init, 275K bss, 13760K reserved, 0K cma-reserved, 1048576K highmem) b: Memory: 1559112K/1572864K available (3519K kernel code, 594K rwdata, 752K rodata, 136K init, 280K bss, 13752K reserved, 0K cma-reserved, 1048576K highmem) Link: https://lkml.kernel.org/r/20201101170454.9567-11-rppt@kernel.org Signed-off-by: Mike Rapoport Cc: Alexey Dobriyan Cc: Catalin Marinas Cc: Geert Uytterhoeven Cc: Greg Ungerer Cc: John Paul Adrian Glaubitz Cc: Jonathan Corbet Cc: Matt Turner Cc: Meelis Roos Cc: Michael Schmitz Cc: Russell King Cc: Tony Luck Cc: Vineet Gupta Cc: Will Deacon Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- arch/arc/include/asm/page.h | 20 +++++++++++++++++--- 1 file changed, 17 insertions(+), 3 deletions(-) (limited to 'arch/arc/include/asm') diff --git a/arch/arc/include/asm/page.h b/arch/arc/include/asm/page.h index b0dfed0f12be..23e41e890eda 100644 --- a/arch/arc/include/asm/page.h +++ b/arch/arc/include/asm/page.h @@ -82,11 +82,25 @@ typedef pte_t * pgtable_t; */ #define virt_to_pfn(kaddr) (__pa(kaddr) >> PAGE_SHIFT) -#define ARCH_PFN_OFFSET virt_to_pfn(CONFIG_LINUX_RAM_BASE) +/* + * When HIGHMEM is enabled we have holes in the memory map so we need + * pfn_valid() that takes into account the actual extents of the physical + * memory + */ +#ifdef CONFIG_HIGHMEM + +extern unsigned long arch_pfn_offset; +#define ARCH_PFN_OFFSET arch_pfn_offset + +extern int pfn_valid(unsigned long pfn); +#define pfn_valid pfn_valid -#ifdef CONFIG_FLATMEM +#else /* CONFIG_HIGHMEM */ + +#define ARCH_PFN_OFFSET virt_to_pfn(CONFIG_LINUX_RAM_BASE) #define pfn_valid(pfn) (((pfn) - ARCH_PFN_OFFSET) < max_mapnr) -#endif + +#endif /* CONFIG_HIGHMEM */ /* * __pa, __va, virt_to_page (ALERT: deprecated, don't use them) -- cgit v1.2.3