Messages in this thread | | | Date | Thu, 28 Mar 2024 19:08:47 -0400 | From | Eric Chanudet <> | Subject | Re: [PATCH v1 0/3] Speed up boot with faster linear map creation |
| |
On Wed, Mar 27, 2024 at 07:12:06PM +0000, Ryan Roberts wrote: > On 26/03/2024 10:14, 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%) > > I've just appended an additional patch to this series. This takes us to a ~95% > reduction overall: > > | 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%) > batch-barriers | 11 (-93%) | 61 (-97%) | 261 (-97%) | 837 (-95%) > > Don't believe the intermediate block-based pgtable idea will now be neccessary > so I don't intend to persue that. It might be that we choose to drop the middle > two patchs; I'm keen to hear opinions. >
Applied on v6.9-rc1, I have much shorter base timing on a similar machine (Ampere HR350A). no-alloc-remap didn't show much difference either.
| SA8775p-ride | Ampere HR350A| | VM, 36G | Metal, 256G | ---------------|--------------|--------------| | ms (%) | ms (%) | ---------------|--------------|--------------| base | 358 (0%) | 2213 (0%) | no-cont-remap | 232 (-35%) | 1283 (-42%) | no-alloc-remap | 228 (-36%) | 1282 (-42%) | lazy-unmap | 231 (-35%) | 1248 (-44%) | batch-barriers | 25 (-93%) | 204 (-91%) |
Tested-By: Eric Chanudet <echanude@redhat.com>
> > 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. > > > > 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 > > >
-- Eric Chanudet
| |