[PATCH -V5 00/25] THP support for PPC64
Aneesh Kumar K.V
aneesh.kumar at linux.vnet.ibm.com
Thu Apr 4 16:57:38 EST 2013
Hi,
This patchset adds transparent hugepage support for PPC64.
TODO:
* hash preload support in update_mmu_cache_pmd (we don't do that for hugetlb)
Some numbers:
The latency measurements code from Anton found at
http://ozlabs.org/~anton/junkcode/latency2001.c
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.
Another test that does 50000000 random access over 1GB area goes from
2.65 seconds to 1.07 seconds with this patchset.
split_huge_page impact:
---------------------
To look at the performance impact of large page invalidate, I tried the below
experiment. The test involved, accessing a large contiguous region of memory
location as below
for (i = 0; i < size; i += PAGE_SIZE)
data[i] = i;
We wanted to access the data in sequential order so that we look at the
worst case THP performance. Accesing the data in sequential order implies
we have the Page table cached and overhead of TLB miss is as minimal as
possible. We also don't touch the entire page, because that can result in
cache evict.
After we touched the full range as above, we now call mprotect on each
of that page. A mprotect will result in a hugepage split. This should
allow us to measure the impact of hugepage split.
for (i = 0; i < size; i += PAGE_SIZE)
mprotect(&data[i], PAGE_SIZE, PROT_READ);
Split hugepage impact:
---------------------
THP enabled: 2.851561705 seconds for test completion
THP disable: 3.599146098 seconds for test completion
We are 20.7% better than non THP case even when we have all the large pages split.
Detailed output:
THP enabled:
---------------------------------------
[root at llmp24l02 ~]# cat /proc/vmstat | grep thp
thp_fault_alloc 0
thp_fault_fallback 0
thp_collapse_alloc 0
thp_collapse_alloc_failed 0
thp_split 0
thp_zero_page_alloc 0
thp_zero_page_alloc_failed 0
[root at llmp24l02 ~]# /root/thp/tools/perf/perf stat -e page-faults,dTLB-load-misses ./split-huge-page-mpro 20G
time taken to touch all the data in ns: 2763096913
Performance counter stats for './split-huge-page-mpro 20G':
1,581 page-faults
3,159 dTLB-load-misses
2.851561705 seconds time elapsed
[root at llmp24l02 ~]#
[root at llmp24l02 ~]# cat /proc/vmstat | grep thp
thp_fault_alloc 1279
thp_fault_fallback 0
thp_collapse_alloc 0
thp_collapse_alloc_failed 0
thp_split 1279
thp_zero_page_alloc 0
thp_zero_page_alloc_failed 0
[root at llmp24l02 ~]#
77.05% split-huge-page [kernel.kallsyms] [k] .clear_user_page
7.10% split-huge-page [kernel.kallsyms] [k] .perf_event_mmap_ctx
1.51% split-huge-page split-huge-page-mpro [.] 0x0000000000000a70
0.96% split-huge-page [unknown] [H] 0x000000000157e3bc
0.81% split-huge-page [kernel.kallsyms] [k] .up_write
0.76% split-huge-page [kernel.kallsyms] [k] .perf_event_mmap
0.76% split-huge-page [kernel.kallsyms] [k] .down_write
0.74% split-huge-page [kernel.kallsyms] [k] .lru_add_page_tail
0.61% split-huge-page [kernel.kallsyms] [k] .split_huge_page
0.59% split-huge-page [kernel.kallsyms] [k] .change_protection
0.51% split-huge-page [kernel.kallsyms] [k] .release_pages
0.96% split-huge-page [unknown] [H] 0x000000000157e3bc
|
|--79.44%-- reloc_start
| |
| |--86.54%-- .__pSeries_lpar_hugepage_invalidate
| | .pSeries_lpar_hugepage_invalidate
| | .hpte_need_hugepage_flush
| | .split_huge_page
| | .__split_huge_page_pmd
| | .vma_adjust
| | .vma_merge
| | .mprotect_fixup
| | .SyS_mprotect
THP disabled:
---------------
[root at llmp24l02 ~]# echo never > /sys/kernel/mm/transparent_hugepage/enabled
[root at llmp24l02 ~]# /root/thp/tools/perf/perf stat -e page-faults,dTLB-load-misses ./split-huge-page-mpro 20G
time taken to touch all the data in ns: 3513767220
Performance counter stats for './split-huge-page-mpro 20G':
3,27,726 page-faults
3,29,654 dTLB-load-misses
3.599146098 seconds time elapsed
[root at llmp24l02 ~]#
Changes from V4:
* Fix bad page error in page_table_alloc
BUG: Bad page state in process stream pfn:f1a59
page:f0000000034dc378 count:1 mapcount:0 mapping: (null) index:0x0
[c000000f322c77d0] [c00000000015e198] .bad_page+0xe8/0x140
[c000000f322c7860] [c00000000015e3c4] .free_pages_prepare+0x1d4/0x1e0
[c000000f322c7910] [c000000000160450] .free_hot_cold_page+0x50/0x230
[c000000f322c79c0] [c00000000003ad18] .page_table_alloc+0x168/0x1c0
Changes from V3:
* PowerNV boot fixes
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.
Thanks,
-aneesh
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