[PATCH v4 2/3] powerpc/mm/hugetlb: Add support for reserving gigantic huge pages via kernel command line

[Aneesh Kumar K.V]

Christophe LEROY <christophe.leroy at c-s.fr> writes:

> Hi,
>
> Le 28/07/2017 à 07:01, Aneesh Kumar K.V a écrit :
>> With commit aa888a74977a8 ("hugetlb: support larger than MAX_ORDER") we added
>> support for allocating gigantic hugepages via kernel command line. Switch
>> ppc64 arch specific code to use that.
>> 
>> W.r.t FSL support, we now limit our allocation range using BOOTMEM_ALLOC_ACCESSIBLE.
>> 
>> We use the kernel command line to do reservation of hugetlb pages on powernv
>> platforms. On pseries hash mmu mode the supported gigantic huge page size is
>> 16GB and that can only be allocated with hypervisor assist. For pseries the
>> command line option doesn't do the allocation. Instead pseries does gigantic
>> hugepage allocation based on hypervisor hint that is specified via
>> "ibm,expected#pages" property of the memory node.
>
> It looks like it doesn't work on the 8xx:
>
> root at vgoip:~# dmesg | grep -i huge
> [    0.000000] Kernel command line: console=ttyCPM0,115200N8 
> ip=172.25.231.25:172.25.231.1::255.0.0.0:vgoip:eth0:off hugepagesz=8M 
> hugepages=4
> [    0.416722] HugeTLB registered 8.00 MiB page size, pre-allocated 4 pages
> [    0.423184] HugeTLB registered 512 KiB page size, pre-allocated 0 pages
> root at vgoip:~# cat /proc/meminfo
> MemTotal:         123388 kB
> MemFree:           77900 kB
> MemAvailable:      78412 kB
> Buffers:               0 kB
> Cached:             3964 kB
> SwapCached:            0 kB
> Active:             3788 kB
> Inactive:           1680 kB
> Active(anon):       1636 kB
> Inactive(anon):       20 kB
> Active(file):       2152 kB
> Inactive(file):     1660 kB
> Unevictable:           0 kB
> Mlocked:               0 kB
> SwapTotal:             0 kB
> SwapFree:              0 kB
> Dirty:                 0 kB
> Writeback:             0 kB
> AnonPages:          1552 kB
> Mapped:             2404 kB
> Shmem:               152 kB
> Slab:                  0 kB
> SReclaimable:          0 kB
> SUnreclaim:            0 kB
> KernelStack:         304 kB
> PageTables:          208 kB
> NFS_Unstable:          0 kB
> Bounce:                0 kB
> WritebackTmp:          0 kB
> CommitLimit:       45308 kB
> Committed_AS:      16664 kB
> VmallocTotal:     866304 kB
> VmallocUsed:           0 kB
> VmallocChunk:          0 kB
> HugePages_Total:       0
> HugePages_Free:        0
> HugePages_Rsvd:        0
> HugePages_Surp:        0
> Hugepagesize:        512 kB

But you are printing above the default hugepaeg details. You haven't
changed that in kernel command line. What does
/sys/kernel/mm/hugepages/<hugepages-size>/nr_hugepages show ?

To change the default hugepage size you may want to use
default_hugepagesz=8M

-aneesh