Messages in this thread | ![/](/images/icornerl.gif) | | Date | Wed, 20 Jan 2021 10:47:37 -0800 | From | Sudarshan Rajagopalan <> | Subject | Re: [PATCH 1/1] arm64: reduce section size for sparsemem |
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On 2021-01-20 09:49, Will Deacon wrote: > On Fri, Jan 08, 2021 at 03:16:00PM -0800, Sudarshan Rajagopalan wrote: >> 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 <sudaraja@codeaurora.org> >> Suggested-by: David Hildenbrand <david@redhat.com> >> Cc: Will Deacon <will@kernel.org> >> Cc: Anshuman Khandual <anshuman.khandual@arm.com> >> Cc: Mike Rapoport <rppt@linux.ibm.com> >> Cc: Mark Rutland <mark.rutland@arm.com> >> Cc: Suren Baghdasaryan <surenb@google.com> >> --- >> 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*/ > > Please can you repost this in light of the comments from Anshuman? > > Thanks, > > Will
Sure Will. We were held up with some other critical tasks.. will repost the patch by EOD after addressing Anshuman's comments.
-- Sudarshan
-- Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a Linux Foundation Collaborative Project
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