Re: [RFC PATCH 10/12] mm: add the buddy system interface

[Kamezawa Hiroyuki]

On 2015/06/25 18:44, Xishi Qiu wrote:
> On 2015/6/10 11:06, Kamezawa Hiroyuki wrote:
>
> > On 2015/06/09 19:04, Xishi Qiu wrote:
> > > On 2015/6/9 15:12, Kamezawa Hiroyuki wrote:
> > >
> > > > On 2015/06/04 22:04, Xishi Qiu wrote:
> > > > > Add the buddy system interface for address range mirroring feature.
> > > > > Allocate mirrored pages in MIGRATE_MIRROR list. If there is no mirrored pages
> > > > > left, use other types pages.
> > > > >
> > > > > Signed-off-by: Xishi Qiu <qiuxishi@xxxxxxxxxx>
> > > > > ---
> > > > >     mm/page_alloc.c | 40 +++++++++++++++++++++++++++++++++++++++-
> > > > >     1 file changed, 39 insertions(+), 1 deletion(-)
> > > > >
> > > > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> > > > > index d4d2066..0fb55288 100644
> > > > > --- a/mm/page_alloc.c
> > > > > +++ b/mm/page_alloc.c
> > > > > @@ -599,6 +599,26 @@ static inline bool is_mirror_pfn(unsigned long pfn)
> > > > >
> > > > >         return false;
> > > > >     }
> > > > > +
> > > > > +static inline bool change_to_mirror(gfp_t gfp_flags, int high_zoneidx)
> > > > > +{
> > > > > +    /*
> > > > > +     * Do not alloc mirrored memory below 4G, because 0-4G is
> > > > > +     * all mirrored by default, and the list is always empty.
> > > > > +     */
> > > > > +    if (high_zoneidx < ZONE_NORMAL)
> > > > > +        return false;
> > > > > +
> > > > > +    /* Alloc mirrored memory for only kernel */
> > > > > +    if (gfp_flags & __GFP_MIRROR)
> > > > > +        return true;
> > > >
> > > > GFP_KERNEL itself should imply mirror, I think.
> > >
> > > Hi Kame,
> > >
> > > How about like this: #define GFP_KERNEL (__GFP_WAIT | __GFP_IO | __GFP_FS | __GFP_MIRROR) ?
> >
> > Hm.... it cannot cover GFP_ATOMIC at el.
> >
> > I guess, mirrored memory should be allocated if !__GFP_HIGHMEM or !__GFP_MOVABLE
>
>
> Hi Kame,
>
> Can we distinguish allocations form user or kernel only by GFP flags?

Allocation from user and file caches are now *always* done with __GFP_MOVABLE.

By this, pages will be allocated from MIGRATE_MOVABLE migration type.
MOVABLE migration type means it's can
be the target for page compaction or memory-hot-remove.

Thanks,
-Kame







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