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Message-ID: <Zg+qwooaWFNL7KIg@vm3>
Date: Fri, 5 Apr 2024 16:39:46 +0900
From: Itaru Kitayama <itaru.kitayama@...ux.dev>
To: Ryan Roberts <ryan.roberts@....com>
Cc: Catalin Marinas <catalin.marinas@....com>,
Will Deacon <will@...nel.org>, Mark Rutland <mark.rutland@....com>,
Ard Biesheuvel <ardb@...nel.org>,
David Hildenbrand <david@...hat.com>,
Donald Dutile <ddutile@...hat.com>,
Eric Chanudet <echanude@...hat.com>,
linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 0/4] Speed up boot with faster linear map creation
On Thu, Apr 04, 2024 at 03:33:04PM +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 | 153 (0%) | 2227 (0%) | 8798 (0%) | 17442 (0%)
> no-cont-remap | 77 (-49%) | 431 (-81%) | 1727 (-80%) | 3796 (-78%)
> batch-barriers | 13 (-92%) | 162 (-93%) | 655 (-93%) | 1656 (-91%)
> no-alloc-remap | 11 (-93%) | 109 (-95%) | 449 (-95%) | 1257 (-93%)
> lazy-unmap | 6 (-96%) | 61 (-97%) | 257 (-97%) | 838 (-95%)
>
> 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 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/
>
> Thanks,
> Ryan
>
>
> Ryan Roberts (4):
> 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
> arm64: mm: Lazily clear pte table mappings from fixmap
>
> arch/arm64/include/asm/fixmap.h | 5 +-
> arch/arm64/include/asm/mmu.h | 8 +
> arch/arm64/include/asm/pgtable.h | 13 +-
> arch/arm64/kernel/cpufeature.c | 10 +-
> arch/arm64/mm/fixmap.c | 11 +
> arch/arm64/mm/mmu.c | 377 +++++++++++++++++++++++--------
> 6 files changed, 319 insertions(+), 105 deletions(-)
>
> --
> 2.25.1
>
I've build and boot tested the v2 on FVP, base is taken from your
linux-rr repo. Running run_vmtests.sh on v2 left some gup longterm not oks, would you take a look at it? The mm ksefltests used is from your linux-rr repo too.
Thanks,
Itaru.
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