[PATCH -V3 00/25] THP support for PPC64

Aneesh Kumar K.V aneesh.kumar at linux.vnet.ibm.com
Fri Mar 15 20:39:42 EST 2013


This patchset adds transparent hugepage support for PPC64.

* powernv still doesn't boot
* hash preload support in update_mmu_cache_pmd

Some numbers:

The latency measurements code from Anton  found at

THP disabled 64K page size
[root at llmp24l02 ~]# ./latency2001 8G
 8589934592    731.73 cycles    205.77 ns
[root at llmp24l02 ~]# ./latency2001 8G
 8589934592    743.39 cycles    209.05 ns
[root at llmp24l02 ~]#

THP disabled large page via hugetlbfs
[root at llmp24l02 ~]# ./latency2001  -l 8G
 8589934592    416.09 cycles    117.01 ns
[root at llmp24l02 ~]# ./latency2001  -l 8G
 8589934592    415.74 cycles    116.91 ns

THP enabled 64K page size.
[root at llmp24l02 ~]# ./latency2001 8G
 8589934592    405.07 cycles    113.91 ns
[root at llmp24l02 ~]# ./latency2001 8G
 8589934592    411.82 cycles    115.81 ns
[root at llmp24l02 ~]#

We are close to hugetlbfs in latency and we can achieve this with zero
config/page reservation. Most of the allocations above are fault allocated.
I haven't really measured the collapse alloc impact.

Another test that does 50000000 random access over 1GB area goes from
2.65 seconds to 1.07 seconds with this patchset.

Change from V2:
* Change patch "powerpc: Reduce PTE table memory wastage" to use much simpler approach
  for PTE page sharing.
* Changes to handle huge pages in KVM code.
* Address other review comments

Changes from V1
* Address review comments
* More patch split
* Add batch hpte invalidate for hugepages.

Changes from RFC V2:
* Address review comments
* More code cleanup and patch split

Changes from RFC V1:
* HugeTLB fs now works
* Compile issues fixed
* rebased to v3.8
* Patch series reorded so that ppc64 cleanups and MM THP changes are moved
  early in the series. This should help in picking those patches early.


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