Re: [PATCH v3 5/5] powerpc/mm: Fix growth direction for hugepages mmaps with slice

[Christophe LEROY]

Le 24/01/2018 Ã 10:15, Aneesh Kumar K.V a ÃcritÂ:
> On 01/24/2018 02:32 PM, Christophe Leroy wrote:
> > An application running with libhugetlbfs fails to allocate
> > additional pages to HEAP due to the hugemap being done
> > inconditionally as topdown mapping:
> >
> > mmap(0x10080000, 1572864, PROT_READ|PROT_WRITE, 
> > MAP_PRIVATE|MAP_ANONYMOUS|0x40000, -1, 0) = 0x73e80000
> > [...]
> > mmap(0x74000000, 1048576, PROT_READ|PROT_WRITE, 
> > MAP_PRIVATE|MAP_ANONYMOUS|0x40000, -1, 0x180000) = 0x73d80000
> > munmap(0x73d80000, 1048576)ÂÂÂÂÂÂÂÂÂÂÂÂ = 0
> > [...]
> > mmap(0x74000000, 1572864, PROT_READ|PROT_WRITE, 
> > MAP_PRIVATE|MAP_ANONYMOUS|0x40000, -1, 0x180000) = 0x73d00000
> > munmap(0x73d00000, 1572864)ÂÂÂÂÂÂÂÂÂÂÂÂ = 0
> > [...]
> > mmap(0x74000000, 1572864, PROT_READ|PROT_WRITE, 
> > MAP_PRIVATE|MAP_ANONYMOUS|0x40000, -1, 0x180000) = 0x73d00000
> > munmap(0x73d00000, 1572864)ÂÂÂÂÂÂÂÂÂÂÂÂ = 0
> > [...]
> >
> > As one can see from the above strace log, mmap() allocates further
> > pages below the initial one because no space is available on top of it.
> >
> > This patch fixes it by requesting bottomup mapping as the non
> > generic hugetlb_get_unmapped_area() does
> >
> > Fixes: d0f13e3c20b6f ("[POWERPC] Introduce address space "slices" ")
> > Signed-off-by: Christophe Leroy <christophe.leroy@xxxxxx>
> > ---
> > Â v3: Was a standalone patch before, but conflicts with this serie.
> >
> > Â arch/powerpc/mm/hugetlbpage.c | 2 +-
> > Â 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/arch/powerpc/mm/hugetlbpage.c 
> > b/arch/powerpc/mm/hugetlbpage.c
> > index 79e1378ee303..368ea6b248ad 100644
> > --- a/arch/powerpc/mm/hugetlbpage.c
> > +++ b/arch/powerpc/mm/hugetlbpage.c
> > @@ -558,7 +558,7 @@ unsigned long hugetlb_get_unmapped_area(struct 
> > file *file, unsigned long addr,
> > ÂÂÂÂÂÂÂÂÂ return radix__hugetlb_get_unmapped_area(file, addr, len,
> > ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ pgoff, flags);
> > Â #endif
> > -ÂÂÂ return slice_get_unmapped_area(addr, len, flags, mmu_psize, 1);
> > +ÂÂÂ return slice_get_unmapped_area(addr, len, flags, mmu_psize, 0);
> > Â }
> > Â #endif
>
> Why make this change also for PPC64? Can you do this #ifdef 8xx?.You can 
> ideally move hugetlb_get_unmapped_area to slice.h and then make this 
> much simpler for 8xxx?

Did you try with HUGETLB_MORECORE_HEAPBASE=0x11000000 on PPC64 as I 
suggested in my last email on this subject (22/01/2018 9:22) ?

Before doing anything specific to the PPC32/8xx, I'd like to be sure the 
issue is definitly only on PPC32.

Thanks,
Christophe