| Message ID | 20240412131908.433043-1-ryan.roberts@arm.com (mailing list archive) |
|---|---|
| Headers | show |
| Series | Speed up boot with faster linear map creation | expand |
On Fri, Apr 12, 2024 at 05:06:41PM +0100, Will Deacon wrote: > On Fri, 12 Apr 2024 14:19:05 +0100, Ryan Roberts wrote: > > It turns out that creating the linear map can take a significant proportion of > > the total boot time, especially when rodata=full. And most of the time is spent > > waiting on superfluous tlb invalidation and memory barriers. This series reworks > > the kernel pgtable generation code to significantly reduce the number of those > > TLBIs, ISBs and DSBs. See each patch for details. > > > > The below shows the execution time of map_mem() across a couple of different > > systems with different RAM configurations. We measure after applying each patch > > and show the improvement relative to base (v6.9-rc2): > > > > [...] > > Applied to arm64 (for-next/mm), thanks! > > [1/3] arm64: mm: Don't remap pgtables per-cont(pte|pmd) block > https://git.kernel.org/arm64/c/5c63db59c5f8 > [2/3] arm64: mm: Batch dsb and isb when populating pgtables > https://git.kernel.org/arm64/c/1fcb7cea8a5f > [3/3] arm64: mm: Don't remap pgtables for allocate vs populate > https://git.kernel.org/arm64/c/0e9df1c905d8 I confirm this series boots the system on FVP (with my .config and my buildroot rootfs using Shrinkwrap). Tested-by: Itaru Kitayama <itaru.kitayama@fujitsu.com> Thanks, Itaru. > > Cheers, > -- > Will > > https://fixes.arm64.dev > https://next.arm64.dev > https://will.arm64.dev
On Fri, Apr 12, 2024 at 02:19:05PM +0100, Ryan Roberts wrote: > Hi All, > > It turns out that creating the linear map can take a significant proportion of > the total boot time, especially when rodata=full. And most of the time is spent > waiting on superfluous tlb invalidation and memory barriers. This series reworks > the kernel pgtable generation code to significantly reduce the number of those > TLBIs, ISBs and DSBs. See each patch for details. > > The below shows the execution time of map_mem() across a couple of different > systems with different RAM configurations. We measure after applying each patch > and show the improvement relative to base (v6.9-rc2): > > | Apple M2 VM | Ampere Altra| Ampere Altra| Ampere Altra > | VM, 16G | VM, 64G | VM, 256G | Metal, 512G > ---------------|-------------|-------------|-------------|------------- > | ms (%) | ms (%) | ms (%) | ms (%) > ---------------|-------------|-------------|-------------|------------- > base | 168 (0%) | 2198 (0%) | 8644 (0%) | 17447 (0%) > no-cont-remap | 78 (-53%) | 435 (-80%) | 1723 (-80%) | 3779 (-78%) > batch-barriers | 11 (-93%) | 161 (-93%) | 656 (-92%) | 1654 (-91%) > no-alloc-remap | 10 (-94%) | 104 (-95%) | 438 (-95%) | 1223 (-93%) > > This series applies on top of v6.9-rc2. All mm selftests pass. I've compile and > boot tested various PAGE_SIZE and VA size configs. Nice! > Ryan Roberts (3): > arm64: mm: Don't remap pgtables per-cont(pte|pmd) block > arm64: mm: Batch dsb and isb when populating pgtables > arm64: mm: Don't remap pgtables for allocate vs populate For the series: Reviewed-by: Mark Rutland <mark.rutland@arm.com> Catalin, Will, are you happy to pick this up? Mark.
On Fri, 12 Apr 2024 at 15:19, Ryan Roberts <ryan.roberts@arm.com> wrote: > > Hi All, > > It turns out that creating the linear map can take a significant proportion of > the total boot time, especially when rodata=full. And most of the time is spent > waiting on superfluous tlb invalidation and memory barriers. This series reworks > the kernel pgtable generation code to significantly reduce the number of those > TLBIs, ISBs and DSBs. See each patch for details. > > The below shows the execution time of map_mem() across a couple of different > systems with different RAM configurations. We measure after applying each patch > and show the improvement relative to base (v6.9-rc2): > > | Apple M2 VM | Ampere Altra| Ampere Altra| Ampere Altra > | VM, 16G | VM, 64G | VM, 256G | Metal, 512G > ---------------|-------------|-------------|-------------|------------- > | ms (%) | ms (%) | ms (%) | ms (%) > ---------------|-------------|-------------|-------------|------------- > base | 168 (0%) | 2198 (0%) | 8644 (0%) | 17447 (0%) > no-cont-remap | 78 (-53%) | 435 (-80%) | 1723 (-80%) | 3779 (-78%) > batch-barriers | 11 (-93%) | 161 (-93%) | 656 (-92%) | 1654 (-91%) > no-alloc-remap | 10 (-94%) | 104 (-95%) | 438 (-95%) | 1223 (-93%) > > This series applies on top of v6.9-rc2. All mm selftests pass. I've compile and > boot tested various PAGE_SIZE and VA size configs. ... > > Ryan Roberts (3): > arm64: mm: Don't remap pgtables per-cont(pte|pmd) block > arm64: mm: Batch dsb and isb when populating pgtables > arm64: mm: Don't remap pgtables for allocate vs populate > For the series, Reviewed-by: Ard Biesheuvel <ardb@kernel.org>
On Fri, 12 Apr 2024 14:19:05 +0100, Ryan Roberts wrote: > It turns out that creating the linear map can take a significant proportion of > the total boot time, especially when rodata=full. And most of the time is spent > waiting on superfluous tlb invalidation and memory barriers. This series reworks > the kernel pgtable generation code to significantly reduce the number of those > TLBIs, ISBs and DSBs. See each patch for details. > > The below shows the execution time of map_mem() across a couple of different > systems with different RAM configurations. We measure after applying each patch > and show the improvement relative to base (v6.9-rc2): > > [...] Applied to arm64 (for-next/mm), thanks! [1/3] arm64: mm: Don't remap pgtables per-cont(pte|pmd) block https://git.kernel.org/arm64/c/5c63db59c5f8 [2/3] arm64: mm: Batch dsb and isb when populating pgtables https://git.kernel.org/arm64/c/1fcb7cea8a5f [3/3] arm64: mm: Don't remap pgtables for allocate vs populate https://git.kernel.org/arm64/c/0e9df1c905d8 Cheers,
Hi All, It turns out that creating the linear map can take a significant proportion of the total boot time, especially when rodata=full. And most of the time is spent waiting on superfluous tlb invalidation and memory barriers. This series reworks the kernel pgtable generation code to significantly reduce the number of those TLBIs, ISBs and DSBs. See each patch for details. The below shows the execution time of map_mem() across a couple of different systems with different RAM configurations. We measure after applying each patch and show the improvement relative to base (v6.9-rc2): | Apple M2 VM | Ampere Altra| Ampere Altra| Ampere Altra | VM, 16G | VM, 64G | VM, 256G | Metal, 512G ---------------|-------------|-------------|-------------|------------- | ms (%) | ms (%) | ms (%) | ms (%) ---------------|-------------|-------------|-------------|------------- base | 168 (0%) | 2198 (0%) | 8644 (0%) | 17447 (0%) no-cont-remap | 78 (-53%) | 435 (-80%) | 1723 (-80%) | 3779 (-78%) batch-barriers | 11 (-93%) | 161 (-93%) | 656 (-92%) | 1654 (-91%) no-alloc-remap | 10 (-94%) | 104 (-95%) | 438 (-95%) | 1223 (-93%) This series applies on top of v6.9-rc2. All mm selftests pass. I've compile and boot tested various PAGE_SIZE and VA size configs. --- Changes since v2 [2] ==================== - Independently increment ptep/pmdp in alloc_init_cont_[pte|pmd]() rather than return the incremented value from int_[pte|pmd]() (per Mark) - Removed explicit barriers from alloc_init_cont_pte() and instead rely on the barriers in pte_clear_fixmap() (per Mark) - Significantly simplify approach to avoiding fixmap during alloc (patch 3 reworked) (per Mark) - Dropped patch 4 - not possible with simplified patch 3 and improvement (~2%) didn't warrant complexity (per Mark) Changes since v1 [1] ==================== - Added Tested-by tags (thanks to Eric and Itaru) - Renamed ___set_pte() -> __set_pte_nosync() (per Ard) - Reordered patches (biggest impact & least controversial first) - Reordered alloc/map/unmap functions in mmu.c to aid reader - pte_clear() -> __pte_clear() in clear_fixmap_nosync() - Reverted generic p4d_index() which caused x86 build error. Replaced with unconditional p4d_index() define under arm64. [1] https://lore.kernel.org/linux-arm-kernel/20240326101448.3453626-1-ryan.roberts@arm.com/ [2] https://lore.kernel.org/linux-arm-kernel/20240404143308.2224141-1-ryan.roberts@arm.com/ Thanks, Ryan Ryan Roberts (3): arm64: mm: Don't remap pgtables per-cont(pte|pmd) block arm64: mm: Batch dsb and isb when populating pgtables arm64: mm: Don't remap pgtables for allocate vs populate arch/arm64/include/asm/pgtable.h | 9 ++- arch/arm64/mm/mmu.c | 101 +++++++++++++++++-------------- 2 files changed, 65 insertions(+), 45 deletions(-) -- 2.25.1