Re: [PATCH] powerpc/mm: Implemented default_hugepagesz verification for powerpc

[victora]

Em 2017-07-05 13:03, victora escreveu:
> Em 2017-07-05 01:26, Aneesh Kumar K.V escreveu:
> > On Tuesday 04 July 2017 01:35 AM, Victor Aoqui wrote:
> > > Implemented default hugepage size verification (default_hugepagesz=)
> > > in order to allow allocation of defined number of pages (hugepages=)
> > > only for supported hugepage sizes.
> > >
> > > Signed-off-by: Victor Aoqui <victora@xxxxxxxxxx>
> > > ---
> > >   arch/powerpc/mm/hugetlbpage.c | 15 +++++++++++++++
> > >   1 file changed, 15 insertions(+)
> > >
> > > diff --git a/arch/powerpc/mm/hugetlbpage.c 
> > > b/arch/powerpc/mm/hugetlbpage.c
> > > index a4f33de..464e72e 100644
> > > --- a/arch/powerpc/mm/hugetlbpage.c
> > > +++ b/arch/powerpc/mm/hugetlbpage.c
> > > @@ -797,6 +797,21 @@ static int __init hugepage_setup_sz(char *str)
> > >   }
> > >   __setup("hugepagesz=", hugepage_setup_sz);
> > >
> > > +static int __init default_hugepage_setup_sz(char *str)
> > > +{
> > > +        unsigned long long size;
> > > +
> > > +        size = memparse(str, &str);
> > > +
> > > +        if (add_huge_page_size(size) != 0) {
> > > +                hugetlb_bad_size();
> > > +                pr_err("Invalid default huge page size 
> > > specified(%llu)\n", size);
> > > +        }
> > > +
> > > +        return 1;
> > > +}
> > > +__setup("default_hugepagesz=", default_hugepage_setup_sz);
> >
> > isn't that a behavior change in what we have now ? . Right now if size
> > specified is not supported, we fallback to HPAGE_SIZE.
>
> Yes, it is. However, is this a correct behavior? If we specify an
> unsupported value, for example default_hugepagesz=1M and
> hugepages=1000, 1M will be ignored and 1000 pages of 16M (arch
> default) will be allocated. This could lead to non-expected out of of
> memory/performance issue.
>
> > mm/hugetlb.c
> >
> > if (!size_to_hstate(default_hstate_size)) {
> > 	default_hstate_size = HPAGE_SIZE;
> > 	if (!size_to_hstate(default_hstate_size))
> > 		hugetlb_add_hstate(HUGETLB_PAGE_ORDER);
> > }
> >
> >
> > > +
> > >   struct kmem_cache *hugepte_cache;
> > >   static int __init hugetlbpage_init(void)
> > >   {
> >
> > Even if we want to do this, this should be done in generic code and
> > should not be powerpc specific
>
> The verification of supported powerpc hugepage size (hugepagesz=) is
> being performed on add_huge_page_size(), which is currently defined in
> arch/powerpc/mm/hugetlbpage.c. I think it makes more sense to
> implement default_hugepagesz= verification on arch/powerpc, don't you
> think?
>
> > -aneesh

Hi Aneesh,

Did you have time to review the comments above?

Thanks
Victor