From: Mike Rapoport <rppt@linux.ibm.com> To: Will Deacon <will@kernel.org> Cc: Wei Li <liwei213@huawei.com>, catalin.marinas@arm.com, fengbaopeng2@hisilicon.com, nsaenzjulienne@suse.de, steve.capper@arm.com, song.bao.hua@hisilicon.com, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, butao@hisilicon.com Subject: Re: [PATCH] arm64: mm: decrease the section size to reduce the memory reserved for the page map Date: Fri, 4 Dec 2020 13:44:00 +0200 [thread overview] Message-ID: <20201204114400.GT123287@linux.ibm.com> (raw) In-Reply-To: <20201204111347.GA844@willie-the-truck> On Fri, Dec 04, 2020 at 11:13:47AM +0000, Will Deacon wrote: > On Fri, Dec 04, 2020 at 09:44:43AM +0800, Wei Li wrote: > > 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> > > --- > > 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 > > We chose '30' to avoid running out of bits in the page flags. What changed? I think that for 64-bit there are still plenty of free bits. I didn't check now, but when I played with SPARSEMEM on m68k there were 8 bits for section out of 32. > With this patch, I can trigger: > > ./include/linux/mmzone.h:1170:2: error: Allocator MAX_ORDER exceeds SECTION_SIZE > #error Allocator MAX_ORDER exceeds SECTION_SIZE > > if I bump up NR_CPUS and NODES_SHIFT. I don't think it's related to NR_CPUS and NODES_SHIFT. This seems rather 64K pages that cause this. Not that is shouldn't be addressed. > Will -- Sincerely yours, Mike.
WARNING: multiple messages have this Message-ID (diff)
From: Mike Rapoport <rppt@linux.ibm.com> To: Will Deacon <will@kernel.org> Cc: song.bao.hua@hisilicon.com, linux-arm-kernel@lists.infradead.org, steve.capper@arm.com, catalin.marinas@arm.com, linux-kernel@vger.kernel.org, Wei Li <liwei213@huawei.com>, butao@hisilicon.com, nsaenzjulienne@suse.de, fengbaopeng2@hisilicon.com Subject: Re: [PATCH] arm64: mm: decrease the section size to reduce the memory reserved for the page map Date: Fri, 4 Dec 2020 13:44:00 +0200 [thread overview] Message-ID: <20201204114400.GT123287@linux.ibm.com> (raw) In-Reply-To: <20201204111347.GA844@willie-the-truck> On Fri, Dec 04, 2020 at 11:13:47AM +0000, Will Deacon wrote: > On Fri, Dec 04, 2020 at 09:44:43AM +0800, Wei Li wrote: > > 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> > > --- > > 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 > > We chose '30' to avoid running out of bits in the page flags. What changed? I think that for 64-bit there are still plenty of free bits. I didn't check now, but when I played with SPARSEMEM on m68k there were 8 bits for section out of 32. > With this patch, I can trigger: > > ./include/linux/mmzone.h:1170:2: error: Allocator MAX_ORDER exceeds SECTION_SIZE > #error Allocator MAX_ORDER exceeds SECTION_SIZE > > if I bump up NR_CPUS and NODES_SHIFT. I don't think it's related to NR_CPUS and NODES_SHIFT. This seems rather 64K pages that cause this. Not that is shouldn't be addressed. > Will -- Sincerely yours, Mike. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
next prev parent reply other threads:[~2020-12-04 11:45 UTC|newest] Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top 2020-12-04 1:44 [PATCH] arm64: mm: decrease the section size to reduce the memory reserved for the page map Wei Li 2020-12-04 1:44 ` Wei Li 2020-12-04 1:50 ` Song Bao Hua (Barry Song) 2020-12-04 1:50 ` Song Bao Hua (Barry Song) 2020-12-04 11:13 ` Will Deacon 2020-12-04 11:13 ` Will Deacon 2020-12-04 11:44 ` Mike Rapoport [this message] 2020-12-04 11:44 ` Mike Rapoport 2020-12-07 1:40 ` Song Bao Hua (Barry Song) 2020-12-07 1:40 ` Song Bao Hua (Barry Song) 2020-12-07 7:30 ` Anshuman Khandual 2020-12-07 7:30 ` Anshuman Khandual 2020-12-07 7:47 ` Song Bao Hua (Barry Song) 2020-12-07 7:47 ` Song Bao Hua (Barry Song) 2020-12-07 9:09 ` Ard Biesheuvel 2020-12-07 9:09 ` Ard Biesheuvel 2020-12-07 9:35 ` Marc Zyngier 2020-12-07 9:35 ` Marc Zyngier 2020-12-07 9:42 ` Mike Rapoport 2020-12-07 9:42 ` Mike Rapoport 2020-12-07 9:49 ` Ard Biesheuvel 2020-12-07 9:49 ` Ard Biesheuvel 2020-12-07 10:04 ` Mike Rapoport 2020-12-07 10:04 ` Mike Rapoport 2020-12-07 10:39 ` Anshuman Khandual 2020-12-07 10:39 ` Anshuman Khandual 2020-12-07 12:07 ` Wei Li 2020-12-07 12:07 ` Wei Li
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