RE: [PATCH] arm64: mm: decrease the section size to reduce the memory reserved for the page map
From: Song Bao Hua (Barry Song) <hidden>
Date: 2020-12-04 01:51:41
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-----Original Message----- From: liwei (CM) Sent: Friday, December 4, 2020 2:45 PM To: catalin.marinas@arm.com; rppt@linux.ibm.com; will@kernel.org; liwei (CM) [off-list ref] Cc: fengbaopeng <redacted>; nsaenzjulienne@suse.de; steve.capper@arm.com; Song Bao Hua (Barry Song) [off-list ref]; linux-arm-kernel@lists.infradead.org; linux-kernel@vger.kernel.org; butao [off-list ref] Subject: [PATCH] arm64: mm: decrease the section size to reduce the memory reserved for the page map For the memory hole, sparse memory model that define SPARSEMEM_VMEMMAP do not free the reserved memory for the page map, decrease the section size can reduce the waste of reserved memory. Signed-off-by: Wei Li <redacted> Signed-off-by: Baopeng Feng <redacted> Signed-off-by: Xia Qing <redacted> ---
Reviewed-by: Barry Song <redacted> When page size is 4K, for each 1GB memory, we need 16MB vmemmap; For each 128MB memory, we need 2MB vmemmap. So while we have memory hole like 928MB(1GB-64MB),if SECTION_SIZE_BITS is 30, we waste 15MB; if SECTION_SIZE_BITS is 27, we waste 1MB only.
quoted hunk ↗ jump to hunk
arch/arm64/include/asm/sparsemem.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)diff --git a/arch/arm64/include/asm/sparsemem.hb/arch/arm64/include/asm/sparsemem.h index 1f43fcc79738..8963bd3def28 100644--- a/arch/arm64/include/asm/sparsemem.h +++ b/arch/arm64/include/asm/sparsemem.h@@ -7,7 +7,7 @@ #ifdef CONFIG_SPARSEMEM #define MAX_PHYSMEM_BITS CONFIG_ARM64_PA_BITS -#define SECTION_SIZE_BITS 30 +#define SECTION_SIZE_BITS 27 #endif #endif --2.15.0
Thanks Barry _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel