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Subject: Re: [PATCH v3 5/5] powerpc/mm: Fix growth direction for hugepages
 mmaps with slice
To:     Christophe LEROY <christophe.leroy@c-s.fr>,
        Benjamin Herrenschmidt <benh@kernel.crashing.org>,
        Paul Mackerras <paulus@samba.org>,
        Michael Ellerman <mpe@ellerman.id.au>,
        Scott Wood <oss@buserror.net>
Cc:     linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org
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From:   "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>
Date:   Wed, 24 Jan 2018 15:21:32 +0530
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On 01/24/2018 03:09 PM, Christophe LEROY wrote:
> 
> 
> Le 24/01/2018 à 10:35, Aneesh Kumar K.V a écrit :
>>

>>> 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) ?
>>
>>
>> yes. The test ran fine for me
> 
> You tried with 0x30000000, it works as well on PPC32.
> 
> I'd really like you to try with 0x11000000 which is in the same slice as 
> the 10020000-10030000 range.
> 
> 

Now that explains is better. But then the requested HEAPBASE was not 
free and hence topdown search got an address in the below range.

7efffd000000-7f0000000000 rw-p 00000000 00:0d 1082770 
/anon_hugepage (deleted)


The new range allocated is such that there is no scope for expansion of 
heap if we do a topdown search. But why should that require us to change 
from topdown/bottomup search?


10000000-10010000 r-xp 00000000 fc:00 9044312 
/home/kvaneesh/a.out
10010000-10020000 r--p 00000000 fc:00 9044312 
/home/kvaneesh/a.out
10020000-10030000 rw-p 00010000 fc:00 9044312 
/home/kvaneesh/a.out
7efffd000000-7f0000000000 rw-p 00000000 00:0d 1082770 
/anon_hugepage (deleted)
7ffff2d40000-7ffff7d60000 rw-p 00000000 00:00 0
7ffff7d60000-7ffff7f10000 r-xp 00000000 fc:00 9250090 
/lib/powerpc64le-linux-gnu/libc-2.23.so
7ffff7f10000-7ffff7f20000 r--p 001a0000 fc:00 9250090 
/lib/powerpc64le-linux-gnu/libc-2.23.so
7ffff7f20000-7ffff7f30000 rw-p 001b0000 fc:00 9250090 
/lib/powerpc64le-linux-gnu/libc-2.23.so
7ffff7f40000-7ffff7f60000 r-xp 00000000 fc:00 10754812 
/usr/lib/libhugetlbfs.so.0
7ffff7f60000-7ffff7f70000 r--p 00010000 fc:00 10754812 
/usr/lib/libhugetlbfs.so.0
7ffff7f70000-7ffff7f80000 rw-p 00020000 fc:00 10754812 
/usr/lib/libhugetlbfs.so.0
7ffff7f80000-7ffff7fa0000 r-xp 00000000 00:00 0 
[vdso]
7ffff7fa0000-7ffff7fe0000 r-xp 00000000 fc:00 9250107 
/lib/powerpc64le-linux-gnu/ld-2.23.so
7ffff7fe0000-7ffff7ff0000 r--p 00030000 fc:00 9250107 
/lib/powerpc64le-linux-gnu/ld-2.23.so
7ffff7ff0000-7ffff8000000 rw-p 00040000 fc:00 9250107 
/lib/powerpc64le-linux-gnu/ld-2.23.so
7ffffffd0000-800000000000 rw-p 00000000 00:00 0 
[stack]


For the specific test, one should pass the HEAPBASE value such that it 
can be expanded if required isn't it ?

-aneesh