[PATCH v2] powerpc/mm: Fix growth direction for hugepages mmaps with slice

[Aneesh Kumar K.V]

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Aneesh Kumar K.V <aneesh.kumar at linux.vnet.ibm.com> writes:

> Christophe LEROY <christophe.leroy at c-s.fr> writes:
>
>> Le 17/01/2018 à 04:19, Aneesh Kumar K.V a écrit :
>>> 
>>> 
>>> On 01/16/2018 10:18 PM, Christophe LEROY wrote:
>>>>
>>>>
>>>> Le 16/01/2018 à 17:03, Aneesh Kumar K.V a écrit :
>>>>> Christophe Leroy <christophe.leroy at c-s.fr> writes:
>>>>>
>>>>>> 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)             = 0
>>>>>> [...]
>>>>>> mmap(0x74000000, 1572864, PROT_READ|PROT_WRITE, 
>>>>>> MAP_PRIVATE|MAP_ANONYMOUS|0x40000, -1, 0x180000) = 0x73d00000
>>>>>> munmap(0x73d00000, 1572864)             = 0
>>>>>> [...]
>>>>>> mmap(0x74000000, 1572864, PROT_READ|PROT_WRITE, 
>>>>>> MAP_PRIVATE|MAP_ANONYMOUS|0x40000, -1, 0x180000) = 0x73d00000
>>>>>> munmap(0x73d00000, 1572864)             = 0
>>>>>> [...]
>>>>>>
>>>>>
>>>>> Can you explain the failure details above. I am not sure I understand
>>>>> what to read from the above output.
>>>>
>>>> libhugetlbfs first requests an area of size 1.5Mbytes, at address 
>>>> 0x10080000
>>>> mmap() returns an area at address 0x73e80000
>>>>
>>>> Then libhugetlbfs requests an additional area on top of that, ie at 
>>>> address 0x74000000, to expand the heap.
>>>> But mmap() returns an area at address 0x73d80000, ie under the 
>>>> previous area.
>>>>
>>> 
>>> 
>>> Can you share the test details?. Why does it not fail on book3s64? We 
>>> use topdown search with book3s64.
>>
>> I don't know about book3s64, I only have 8xx.
>>
>> Here is my test app:
>>
>
> The test ran fine on ppc64.
>
> kvaneesh at ltctulc6a-p1:[~]$ HUGETLB_MORECORE=yes ./a.out 
> 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
> 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]
>
>
> Allocated 1Mbytes at 0x10000000010
>
>
> Allocated 1Mbytes at 0x10002000020
>
>
> Allocated 1Mbytes at 0x10004000030
>
> 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
> 10000000000-10003000000 rw-p 00000000 00:0d 1041435                      /anon_hugepage (deleted)
> 10003000000-10005000000 rw-p 03000000 00:0d 1041436                      /anon_hugepage (deleted)
> 10005000000-10007000000 rw-p 05000000 00:0d 1041437                      /anon_hugepage (deleted)
> 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]
>
>
>
> So i am definitely missing something. I understand that generic hugetlb
> get unmapped area always search bottom up and 8xx used to depend on that
> callback. But on ppc64 slice based get unmapped area always did topdown
> and I am not sure whether we should change that. More over I don't think
> MAP_GROWSDOWN is the right flag for selecting topdown/bottom up search.
>
>
> Is it that libhugetlbfs does something specific for 32 bit? Other option
> is to add huget_get_unmapped_area for 8xx that does bottom up search?
>
> If you are on ppc64 irc on freenode we can discuss this there.
> -aneesh