Messages in this thread | | | From | Ard Biesheuvel <> | Date | Wed, 27 Mar 2024 12:09:44 +0200 | Subject | Re: [PATCH v1 0/3] Speed up boot with faster linear map creation |
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Hi Ryan,
On Tue, 26 Mar 2024 at 12:15, 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 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. >
These are very nice results!
Before digging into the details: do we still have a strong case for supporting contiguous PTEs and PMDs in these routines?
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