Messages in this thread | | | Subject | Re: [PATCH v3 5/5] powerpc/mm: Fix growth direction for hugepages mmaps with slice | From | Christophe LEROY <> | Date | Wed, 24 Jan 2018 11:19:56 +0100 |
| |
Le 24/01/2018 à 11:08, Aneesh Kumar K.V a écrit : > > > On 01/24/2018 03:33 PM, Christophe LEROY wrote: >> >> >> Le 24/01/2018 à 10:51, Aneesh Kumar K.V a écrit : >>> >>> >>> 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 ? >> >> For the test, yes, it is dumb to pass an unusable HEAPBASE, but what >> happens in real life: >> * PPC32: No HEAPBASE, hugetlbfs defines a HEAPBASE at sbrk(0) + >> PAGE_SIZE = 0x10800000 ==> This is in the same slice as already >> allocated ==> the kernel does as if mmap() had been called with no >> hint address and allocates something unusable instead. >> * PPC64: No HEAPBASE, hugetlbfs seems to define a HEAPBASE at >> 100000000000, which doesn't conflict with an already allocated mapping >> ==> it works. >> >> Now, when we take the generic case, ie when slice is not activated, >> when you call mmap() without a hint address, it allocates a suitable >> address because it does bottom-up. Why do differently with slices ? >> > > IIUC that is largely arch dependent, PPC64 always did topdown search. > Even for regular non hugetlb mmap it did topdown search. If you set > legacy mmap we selected bottom up approach. You can check > arch_pick_mmap_layout() for more details. Now x86 is slightly different. > For the default search if we can't find a mapping address it will try a > bottomup search. Having said that if you think libhugetlbfs made > assumptions with respect to 8xx and you don't want to break it make > 8xx unmapped area search bottomup. >
Or would there be a way to make libhugetlbfs aware of the slices constraints and make it choose a suitable hint address at first try ?
Christophe
| |