RE: [PATCH v10 11/12] mm/vmalloc: Hugepage vmalloc mappings

David Laight
2021-01-26T20:12:02Z

From: Christophe Leroy
> Sent: 25 January 2021 09:15
>
> Le 24/01/2021 à 09:22, Nicholas Piggin a écrit :
> > Support huge page vmalloc mappings. Config option HAVE_ARCH_HUGE_VMALLOC
> > enables support on architectures that define HAVE_ARCH_HUGE_VMAP and
> > supports PMD sized vmap mappings.
> >
> > vmalloc will attempt to allocate PMD-sized pages if allocating PMD size
> > or larger, and fall back to small pages if that was unsuccessful.
> >
> > Architectures must ensure that any arch specific vmalloc allocations
> > that require PAGE_SIZE mappings (e.g., module allocations vs strict
> > module rwx) use the VM_NOHUGE flag to inhibit larger mappings.
> >
> > When hugepage vmalloc mappings are enabled in the next patch, this
> > reduces TLB misses by nearly 30x on a `git diff` workload on a 2-node
> > POWER9 (59,800 -> 2,100) and reduces CPU cycles by 0.54%.
> >
> > This can result in more internal fragmentation and memory overhead for a
> > given allocation, an option nohugevmalloc is added to disable at boot.
> >
> > Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
> > ---
> > arch/Kconfig | 10 +++
> > include/linux/vmalloc.h | 18 ++++
> > mm/page_alloc.c | 5 +-
> > mm/vmalloc.c | 192 ++++++++++++++++++++++++++++++----------
> > 4 files changed, 177 insertions(+), 48 deletions(-)
> >
>
> > diff --git a/mm/vmalloc.c b/mm/vmalloc.c
> > index 0377e1d059e5..eef61e0f5170 100644
> > --- a/mm/vmalloc.c
> > +++ b/mm/vmalloc.c
>
> > @@ -2691,15 +2746,18 @@ EXPORT_SYMBOL_GPL(vmap_pfn);
> > #endif /* CONFIG_VMAP_PFN */
> >
> > static void *__vmalloc_area_node(struct vm_struct *area, gfp_t gfp_mask,
> > - pgprot_t prot, int node)
> > + pgprot_t prot, unsigned int page_shift,
> > + int node)
> > {
> > const gfp_t nested_gfp = (gfp_mask & GFP_RECLAIM_MASK) | __GFP_ZERO;
> > - unsigned int nr_pages = get_vm_area_size(area) >> PAGE_SHIFT;
> > - unsigned long array_size;
> > - unsigned int i;
> > + unsigned int page_order = page_shift - PAGE_SHIFT;
> > + unsigned long addr = (unsigned long)area->addr;
> > + unsigned long size = get_vm_area_size(area);
> > + unsigned int nr_small_pages = size >> PAGE_SHIFT;
> > struct page **pages;
> > + unsigned int i;
> >
> > - array_size = (unsigned long)nr_pages * sizeof(struct page *);
> > + array_size = (unsigned long)nr_small_pages * sizeof(struct page *);
>
> array_size() is a function in include/linux/overflow.h
>
> For some reason, it breaks the build with your series.

I can't see the replacement definition for array_size.
The old local variable is deleted.

David

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