Re: [PATCH v2 08/23] mm/memblock: Add memblock memory allocationapis

[Grygorii Strashko]

On 12/05/2013 10:34 PM, Santosh Shilimkar wrote:
> Grygorii,
>
> On Thursday 05 December 2013 01:48 PM, Strashko, Grygorii wrote:
> > Hi Tejun,
> >
> > > On Thu, Dec 05, 2013 at 06:35:00PM +0200, Grygorii Strashko wrote:
> > > > > > +#define memblock_virt_alloc_align(x, align) \
> > > > > > +  memblock_virt_alloc_try_nid(x, align, BOOTMEM_LOW_LIMIT, \
> > > > > > +                               BOOTMEM_ALLOC_ACCESSIBLE, MAX_NUMNODES)
> > > > >
> > > > > Also, do we really need this align variant separate when the caller
> > > > > can simply specify 0 for the default?
> > > >
> > > > Unfortunately Yes.
> > > > We need it to keep compatibility with bootmem/nobootmem
> > > > which don't handle 0 as default align value.
> > >
> > > Hmm... why wouldn't just interpreting 0 to SMP_CACHE_BYTES in the
> > > memblock_virt*() function work?
> >
> > Problem is not with memblock_virt*(). The issue will happen in case if
> > memblock or nobootmem are disabled in below code (memblock_virt*() is disabled).
> >
> > +/* Fall back to all the existing bootmem APIs */
> > +#define memblock_virt_alloc(x) \
> > +       __alloc_bootmem(x, SMP_CACHE_BYTES, BOOTMEM_LOW_LIMIT)
> >
> > which will be transformed to
> > +/* Fall back to all the existing bootmem APIs */
> > +#define memblock_virt_alloc(x, align) \
> > +       __alloc_bootmem(x, align, BOOTMEM_LOW_LIMIT)
> >
> > and used as
> >
> > memblock_virt_alloc(size, 0);
> >
> > so, by default bootmem code will use 0 as default alignment and not SMP_CACHE_BYTES
> > and that is wrong.
> Looks like you didn't understood the suggestion completely.
> The fall back inline will look like below .....
>
> static inline memblock_virt_alloc(x, align)
> {
> 	if (align == 0)
> 		align = SMP_CACHE_BYTES
> 	__alloc_bootmem(x, align, BOOTMEM_LOW_LIMIT);
> }

I understand. thanks.

Regards,
-grygorii
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