Re: [PATCH 1/2] mm: cma: NUMA node interface

[Aslan Bakirov <aslanbekirov@gmail.com>]

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On Thu, Apr 2, 2020 at 4:48 PM Vlastimil Babka <vbabka@suse.cz> wrote:

> On 3/26/20 10:27 PM, Aslan Bakirov wrote:
> > I've noticed that there is no interfaces exposed by CMA which would let
> me
> > to declare contigous memory on particular NUMA node.
> >
> > This patchset adds the ability to try to allocate contiguous memory on
> > specific node.
>
> I would say more explicitly that 'try' here means it will fallback to other
> nodes if the specific one doesn't work. At least AFAICS that's what it
> does by
> calling memblock_alloc_range_nid() with exact_nid=false.
>

Thanks for the comments, Vlastimil. I created the next version with
mentioning fallback case in the changelog.

>
> > Implement a new method for declaring contigous memory on particular node
> > and keep cma_declare_contiguous() as a wrapper.
>
> Should there be also support for using this node spcification in the cma=X
> boot
> param?
>
> For this, I would wait for a real usecase for now, because adding it is
easy but removing is hard.


> > Signed-off-by: Aslan Bakirov <aslan@fb.com>
>
> ...
>
> > --- a/mm/cma.c
> > +++ b/mm/cma.c
> > @@ -220,7 +220,7 @@ int __init cma_init_reserved_mem(phys_addr_t base,
> phys_addr_t size,
> >  }
> >
> >  /**
> > - * cma_declare_contiguous() - reserve custom contiguous area
> > + * cma_declare_contiguous_nid() - reserve custom contiguous area
> >   * @base: Base address of the reserved area optional, use 0 for any
> >   * @size: Size of the reserved area (in bytes),
> >   * @limit: End address of the reserved memory (optional, 0 for any).
> > @@ -229,6 +229,7 @@ int __init cma_init_reserved_mem(phys_addr_t base,
> phys_addr_t size,
> >   * @fixed: hint about where to place the reserved area
> >   * @name: The name of the area. See function cma_init_reserved_mem()
> >   * @res_cma: Pointer to store the created cma region.
> > + * @nid: nid of the free area to find, %NUMA_NO_NODE for any node
>
> The bit about fallback should be also specified here.
>
> >   *
> >   * This function reserves memory from early allocator. It should be
> >   * called by arch specific code once the early allocator (memblock or
> bootmem)
> > @@ -238,10 +239,10 @@ int __init cma_init_reserved_mem(phys_addr_t base,
> phys_addr_t size,
> >   * If @fixed is true, reserve contiguous area at exactly @base.  If
> false,
> >   * reserve in range from @base to @limit.
> >   */
> > -int __init cma_declare_contiguous(phys_addr_t base,
> > +int __init cma_declare_contiguous_nid(phys_addr_t base,
> >                       phys_addr_t size, phys_addr_t limit,
> >                       phys_addr_t alignment, unsigned int order_per_bit,
> > -                     bool fixed, const char *name, struct cma **res_cma)
> > +                     bool fixed, const char *name, struct cma
> **res_cma, int nid)
> >  {
> >       phys_addr_t memblock_end = memblock_end_of_DRAM();
> >       phys_addr_t highmem_start;
>
>

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