Re: [RFC PATCH 0/8] mm/vmalloc: Speed up ioremap, vmalloc and vmap with contiguous memory

[Dev Jain <dev.jain@arm.com>]

On 08/04/26 8:21 am, Barry Song (Xiaomi) wrote:
> This patchset accelerates ioremap, vmalloc, and vmap when the memory
> is physically fully or partially contiguous. Two techniques are used:
> 
> 1. Avoid page table zigzag when setting PTEs/PMDs for multiple memory
>    segments
> 2. Use batched mappings wherever possible in both vmalloc and ARM64
>    layers
> 
> Patches 1–2 extend ARM64 vmalloc CONT-PTE mapping to support multiple
> CONT-PTE regions instead of just one.
> 
> Patches 3–4 extend vmap_small_pages_range_noflush() to support page
> shifts other than PAGE_SHIFT. This allows mapping multiple memory
> segments for vmalloc() without zigzagging page tables.
> 
> Patches 5–8 add huge vmap support for contiguous pages. This not only
> improves performance but also enables PMD or CONT-PTE mapping for the
> vmapped area, reducing TLB pressure.
> 
> Many thanks to Xueyuan Chen for his substantial testing efforts
> on RK3588 boards.
> 
> On the RK3588 8-core ARM64 SoC, with tasks pinned to CPU2 and
> the performance CPUfreq policy enabled, Xueyuan’s tests report:
> 
> * ioremap(1 MB): 1.2× faster
> * vmalloc(1 MB) mapping time (excluding allocation) with
>   VM_ALLOW_HUGE_VMAP: 1.5× faster
> * vmap(): 5.6× faster when memory includes some order-8 pages,
>   with no regression observed for order-0 pages
> 
> Barry Song (Xiaomi) (8):
>   arm64/hugetlb: Extend batching of multiple CONT_PTE in a single PTE
>     setup
>   arm64/vmalloc: Allow arch_vmap_pte_range_map_size to batch multiple
>     CONT_PTE
>   mm/vmalloc: Extend vmap_small_pages_range_noflush() to support larger
>     page_shift sizes
>   mm/vmalloc: Eliminate page table zigzag for huge vmalloc mappings
>   mm/vmalloc: map contiguous pages in batches for vmap() if possible
>   mm/vmalloc: align vm_area so vmap() can batch mappings
>   mm/vmalloc: Coalesce same page_shift mappings in vmap to avoid pgtable
>     zigzag
>   mm/vmalloc: Stop scanning for compound pages after encountering small
>     pages in vmap
> 
>  arch/arm64/include/asm/vmalloc.h |   6 +-
>  arch/arm64/mm/hugetlbpage.c      |  10 ++
>  mm/vmalloc.c                     | 178 +++++++++++++++++++++++++------
>  3 files changed, 161 insertions(+), 33 deletions(-)
> 

Hi Barry, have you got the chance to work on v2?