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Groups > linux.kernel > #1713697 > unrolled thread
| Started by | Ingo Molnar <mingo@kernel.org> |
|---|---|
| First post | 2017-08-17 11:10 +0200 |
| Last post | 2017-08-21 17:30 +0200 |
| Articles | 4 — 2 participants |
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Re: [PATCHv4 08/14] x86/mm: Make PGDIR_SHIFT and PTRS_PER_P4D variable Ingo Molnar <mingo@kernel.org> - 2017-08-17 11:10 +0200
Re: [PATCHv4 08/14] x86/mm: Make PGDIR_SHIFT and PTRS_PER_P4D variable "Kirill A. Shutemov" <kirill@shutemov.name> - 2017-08-17 13:00 +0200
Re: [PATCHv4 08/14] x86/mm: Make PGDIR_SHIFT and PTRS_PER_P4D variable Ingo Molnar <mingo@kernel.org> - 2017-08-17 13:20 +0200
Re: [PATCHv4 08/14] x86/mm: Make PGDIR_SHIFT and PTRS_PER_P4D variable "Kirill A. Shutemov" <kirill@shutemov.name> - 2017-08-21 17:30 +0200
| From | Ingo Molnar <mingo@kernel.org> |
|---|---|
| Date | 2017-08-17 11:10 +0200 |
| Subject | Re: [PATCHv4 08/14] x86/mm: Make PGDIR_SHIFT and PTRS_PER_P4D variable |
| Message-ID | <ufoYr-2Kf-59@gated-at.bofh.it> |
* Kirill A. Shutemov <kirill.shutemov@linux.intel.com> wrote: > For boot-time switching between 4- and 5-level paging we need to be able > to fold p4d page table level at runtime. It requires variable > PGDIR_SHIFT and PTRS_PER_P4D. > > Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> > --- > arch/x86/boot/compressed/kaslr.c | 5 +++++ > arch/x86/include/asm/pgtable_32.h | 2 ++ > arch/x86/include/asm/pgtable_32_types.h | 2 ++ > arch/x86/include/asm/pgtable_64_types.h | 15 +++++++++++++-- > arch/x86/kernel/head64.c | 9 ++++++++- > arch/x86/mm/dump_pagetables.c | 12 +++++------- > arch/x86/mm/init_64.c | 2 +- > arch/x86/mm/kasan_init_64.c | 2 +- > arch/x86/platform/efi/efi_64.c | 4 ++-- > include/asm-generic/5level-fixup.h | 1 + > include/asm-generic/pgtable-nop4d.h | 1 + > include/linux/kasan.h | 2 +- > mm/kasan/kasan_init.c | 2 +- > 13 files changed, 43 insertions(+), 16 deletions(-) So I'm wondering what the code generation effect of this is - what's the before/after vmlinux size? My guess is that the effect should be very small, as these constants are not widely used - but I'm only guessing and could be wrong. Thanks, Ingo
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| From | "Kirill A. Shutemov" <kirill@shutemov.name> |
|---|---|
| Date | 2017-08-17 13:00 +0200 |
| Message-ID | <ufqGS-3Hy-3@gated-at.bofh.it> |
| In reply to | #1713697 |
On Thu, Aug 17, 2017 at 11:00:38AM +0200, Ingo Molnar wrote: > > * Kirill A. Shutemov <kirill.shutemov@linux.intel.com> wrote: > > > For boot-time switching between 4- and 5-level paging we need to be able > > to fold p4d page table level at runtime. It requires variable > > PGDIR_SHIFT and PTRS_PER_P4D. > > > > Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> > > --- > > arch/x86/boot/compressed/kaslr.c | 5 +++++ > > arch/x86/include/asm/pgtable_32.h | 2 ++ > > arch/x86/include/asm/pgtable_32_types.h | 2 ++ > > arch/x86/include/asm/pgtable_64_types.h | 15 +++++++++++++-- > > arch/x86/kernel/head64.c | 9 ++++++++- > > arch/x86/mm/dump_pagetables.c | 12 +++++------- > > arch/x86/mm/init_64.c | 2 +- > > arch/x86/mm/kasan_init_64.c | 2 +- > > arch/x86/platform/efi/efi_64.c | 4 ++-- > > include/asm-generic/5level-fixup.h | 1 + > > include/asm-generic/pgtable-nop4d.h | 1 + > > include/linux/kasan.h | 2 +- > > mm/kasan/kasan_init.c | 2 +- > > 13 files changed, 43 insertions(+), 16 deletions(-) > > So I'm wondering what the code generation effect of this is - what's the > before/after vmlinux size? > > My guess is that the effect should be very small, as these constants are not > widely used - but I'm only guessing and could be wrong. This change increase vmlinux size for defconfig + X86_5LEVEL=y by ~4k or 0.01%. -- Kirill A. Shutemov
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| From | Ingo Molnar <mingo@kernel.org> |
|---|---|
| Date | 2017-08-17 13:20 +0200 |
| Message-ID | <ufr0e-44g-13@gated-at.bofh.it> |
| In reply to | #1713818 |
* Kirill A. Shutemov <kirill@shutemov.name> wrote: > On Thu, Aug 17, 2017 at 11:00:38AM +0200, Ingo Molnar wrote: > > > > * Kirill A. Shutemov <kirill.shutemov@linux.intel.com> wrote: > > > > > For boot-time switching between 4- and 5-level paging we need to be able > > > to fold p4d page table level at runtime. It requires variable > > > PGDIR_SHIFT and PTRS_PER_P4D. > > > > > > Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> > > > --- > > > arch/x86/boot/compressed/kaslr.c | 5 +++++ > > > arch/x86/include/asm/pgtable_32.h | 2 ++ > > > arch/x86/include/asm/pgtable_32_types.h | 2 ++ > > > arch/x86/include/asm/pgtable_64_types.h | 15 +++++++++++++-- > > > arch/x86/kernel/head64.c | 9 ++++++++- > > > arch/x86/mm/dump_pagetables.c | 12 +++++------- > > > arch/x86/mm/init_64.c | 2 +- > > > arch/x86/mm/kasan_init_64.c | 2 +- > > > arch/x86/platform/efi/efi_64.c | 4 ++-- > > > include/asm-generic/5level-fixup.h | 1 + > > > include/asm-generic/pgtable-nop4d.h | 1 + > > > include/linux/kasan.h | 2 +- > > > mm/kasan/kasan_init.c | 2 +- > > > 13 files changed, 43 insertions(+), 16 deletions(-) > > > > So I'm wondering what the code generation effect of this is - what's the > > before/after vmlinux size? > > > > My guess is that the effect should be very small, as these constants are not > > widely used - but I'm only guessing and could be wrong. > > This change increase vmlinux size for defconfig + X86_5LEVEL=y by ~4k or > 0.01%. Please add this info to one of the changelogs. BTW., some of that might be won back via the later optimizations, right? BTW, I think what matters most is the .text section size, while 'size' would also add exceptions/out-of-line sections too. Here's a way to display the .text section only: triton:~/tip> printf "# vmlinux .text size: %d\n" 0x$(echo $(readelf -W -e vmlinux | grep ' \[ 1\] .text ') | cut -d' ' -f7) # vmlinux .text size: 9797610 triton:~/tip> size vmlinux text data bss dec hex filename 10748306 4875500 876544 16500350 fbc67e vmlinux Thanks, Ingo
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| From | "Kirill A. Shutemov" <kirill@shutemov.name> |
|---|---|
| Date | 2017-08-21 17:30 +0200 |
| Message-ID | <ugWOm-648-11@gated-at.bofh.it> |
| In reply to | #1713825 |
On Thu, Aug 17, 2017 at 01:10:05PM +0200, Ingo Molnar wrote: > > * Kirill A. Shutemov <kirill@shutemov.name> wrote: > > > On Thu, Aug 17, 2017 at 11:00:38AM +0200, Ingo Molnar wrote: > > > > > > * Kirill A. Shutemov <kirill.shutemov@linux.intel.com> wrote: > > > > > > > For boot-time switching between 4- and 5-level paging we need to be able > > > > to fold p4d page table level at runtime. It requires variable > > > > PGDIR_SHIFT and PTRS_PER_P4D. > > > > > > > > Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> > > > > --- > > > > arch/x86/boot/compressed/kaslr.c | 5 +++++ > > > > arch/x86/include/asm/pgtable_32.h | 2 ++ > > > > arch/x86/include/asm/pgtable_32_types.h | 2 ++ > > > > arch/x86/include/asm/pgtable_64_types.h | 15 +++++++++++++-- > > > > arch/x86/kernel/head64.c | 9 ++++++++- > > > > arch/x86/mm/dump_pagetables.c | 12 +++++------- > > > > arch/x86/mm/init_64.c | 2 +- > > > > arch/x86/mm/kasan_init_64.c | 2 +- > > > > arch/x86/platform/efi/efi_64.c | 4 ++-- > > > > include/asm-generic/5level-fixup.h | 1 + > > > > include/asm-generic/pgtable-nop4d.h | 1 + > > > > include/linux/kasan.h | 2 +- > > > > mm/kasan/kasan_init.c | 2 +- > > > > 13 files changed, 43 insertions(+), 16 deletions(-) > > > > > > So I'm wondering what the code generation effect of this is - what's the > > > before/after vmlinux size? > > > > > > My guess is that the effect should be very small, as these constants are not > > > widely used - but I'm only guessing and could be wrong. > > > > This change increase vmlinux size for defconfig + X86_5LEVEL=y by ~4k or > > 0.01%. > > Please add this info to one of the changelogs. > > BTW., some of that might be won back via the later optimizations, right? Sorry, but no. Just chacked. Introducing alternatives increases .text segment size by about 4k. -- Kirill A. Shutemov
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