Messages in this thread Patch in this message | | | Date | Wed, 27 Mar 2024 11:10:26 +0000 | Subject | Re: [PATCH v1 0/3] Speed up boot with faster linear map creation | From | Ryan Roberts <> |
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On 27/03/2024 11:06, Itaru Kitayama wrote: > On Tue, Mar 26, 2024 at 10:14:45AM +0000, 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 a large portion of the >> time it takes to create the linear map is issuing TLBIs. This series reworks the >> kernel pgtable generation code to significantly reduce the number of TLBIs. 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-rc1): >> >> | Apple M2 VM | Ampere Altra| Ampere Altra| Ampere Altra >> | VM, 16G | VM, 64G | VM, 256G | Metal, 512G >> ---------------|-------------|-------------|-------------|------------- >> | ms (%) | ms (%) | ms (%) | ms (%) >> ---------------|-------------|-------------|-------------|------------- >> base | 151 (0%) | 2191 (0%) | 8990 (0%) | 17443 (0%) >> no-cont-remap | 77 (-49%) | 429 (-80%) | 1753 (-80%) | 3796 (-78%) >> no-alloc-remap | 77 (-49%) | 375 (-83%) | 1532 (-83%) | 3366 (-81%) >> lazy-unmap | 63 (-58%) | 330 (-85%) | 1312 (-85%) | 2929 (-83%) >> >> This series applies on top of v6.9-rc1. All mm selftests pass. I haven't yet >> tested all VA size configs (although I don't anticipate any issues); I'll do >> this as part of followup. > > The series was applied cleanly on top of v6.9-rc1+ of Linus's master > branch, and boots fine on M1 VM with 14GB of memory. > > Just out of curiosity, how did you measure the boot time and obtain the > breakdown of the execution times of each phase?
diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c index 495b732d5af3..8a9d47115784 100644 --- a/arch/arm64/mm/mmu.c +++ b/arch/arm64/mm/mmu.c @@ -792,7 +792,14 @@ static void __init create_idmap(void)
void __init paging_init(void) { + u64 start, end; + + start = __arch_counter_get_cntvct(); map_mem(swapper_pg_dir); + end = __arch_counter_get_cntvct(); + + pr_err("map_mem: time=%llu us\n", + ((end - start) * 1000000) / arch_timer_get_cntfrq());
memblock_allow_resize();
> Tested-by: Itaru Kitayama <itaru.kitayama@fujitsu.com>
Thanks!
> > Thanks, > Itaru. > >> >> Thanks, >> Ryan >> >> >> Ryan Roberts (3): >> arm64: mm: Don't remap pgtables per- cont(pte|pmd) block >> 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 | 4 - >> arch/arm64/kernel/cpufeature.c | 10 +- >> arch/arm64/mm/fixmap.c | 11 + >> arch/arm64/mm/mmu.c | 364 +++++++++++++++++++++++-------- >> include/linux/pgtable.h | 8 + >> 7 files changed, 307 insertions(+), 103 deletions(-) >> >> -- >> 2.25.1 >>
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