Messages in this thread | | | From | "Song Bao Hua (Barry Song)" <> | Subject | RE: [PATCH] arm64: mm: decrease the section size to reduce the memory reserved for the page map | Date | Fri, 4 Dec 2020 01:50:40 +0000 |
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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) > <liwei213@huawei.com> > Cc: fengbaopeng <fengbaopeng2@hisilicon.com>; nsaenzjulienne@suse.de; > steve.capper@arm.com; Song Bao Hua (Barry Song) <song.bao.hua@hisilicon.com>; > linux-arm-kernel@lists.infradead.org; linux-kernel@vger.kernel.org; butao > <butao@hisilicon.com> > 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 <liwei213@huawei.com> > Signed-off-by: Baopeng Feng <fengbaopeng2@hisilicon.com> > Signed-off-by: Xia Qing <saberlily.xia@hisilicon.com> > ---
Reviewed-by: Barry Song <song.bao.hua@hisilicon.com>
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.
> arch/arm64/include/asm/sparsemem.h | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/arch/arm64/include/asm/sparsemem.h > b/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
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