Re: [PATCHv4 00/10] split page table lock for PMD tables

From: Alex Thorlton
Date: Fri Oct 04 2013 - 16:12:13 EST

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Kirill,

I've pasted in my results for 512 cores below. Things are looking
really good here. I don't have a test for HUGETLBFS, but if you want to
pass me the one you used, I can run that too. I suppose I could write
one, but why reinvent the wheel? :)

Sorry for the delay on these results. I hit some strange issues with
running thp_memscale on systems with either of the following
combinations of configuration options set:

[thp off]
HUGETLBFS=y
HUGETLB_PAGE=y
NUMA_BALANCING=y
NUMA_BALANCING_DEFAULT_ENABLED=y

[thp on or off]
HUGETLBFS=n
HUGETLB_PAGE=n
NUMA_BALANCING=y
NUMA_BALANCING_DEFAULT_ENABLED=y

I'm getting segfaults intermittently, as well as some weird RCU sched
errors. This happens in vanilla 3.12-rc2, so it doesn't have anything
to do with your patches, but I thought I'd let you know. There didn't
used to be any issues with this test, so I think there's a subtle kernel
bug here. That's, of course, an entirely separate issue though.

As far as these patches go, I think everything looks good (save for the
bit of discussion you were having with Andrew earlier, which I think
you've worked out). My testing shows that the page fault rates are
actually better on this threaded test than in the non-threaded case!

- Alex

On Fri, Sep 27, 2013 at 04:16:17PM +0300, Kirill A. Shutemov wrote:
> Alex Thorlton noticed that some massively threaded workloads work poorly,
> if THP enabled. This patchset fixes this by introducing split page table
> lock for PMD tables. hugetlbfs is not covered yet.
>
> This patchset is based on work by Naoya Horiguchi.
>
> Please review and consider applying.
>
> Changes:
> v4:
> - convert hugetlb to new locking;
> v3:
> - fix USE_SPLIT_PMD_PTLOCKS;
> - fix warning in fs/proc/task_mmu.c;
> v2:
> - reuse CONFIG_SPLIT_PTLOCK_CPUS for PMD split lock;
> - s/huge_pmd_lock/pmd_lock/g;
> - assume pgtable_pmd_page_ctor() can fail;
> - fix format line in task_mem() for VmPTE;
>
> THP off, v3.12-rc2:
> -------------------
>
> Performance counter stats for './thp_memscale -c 80 -b 512m' (5 runs):
>
> 1037072.835207 task-clock # 57.426 CPUs utilized ( +- 3.59% )
> 95,093 context-switches # 0.092 K/sec ( +- 3.93% )
> 140 cpu-migrations # 0.000 K/sec ( +- 5.28% )
> 10,000,550 page-faults # 0.010 M/sec ( +- 0.00% )
> 2,455,210,400,261 cycles # 2.367 GHz ( +- 3.62% ) [83.33%]
> 2,429,281,882,056 stalled-cycles-frontend # 98.94% frontend cycles idle ( +- 3.67% ) [83.33%]
> 1,975,960,019,659 stalled-cycles-backend # 80.48% backend cycles idle ( +- 3.88% ) [66.68%]
> 46,503,296,013 instructions # 0.02 insns per cycle
> # 52.24 stalled cycles per insn ( +- 3.21% ) [83.34%]
> 9,278,997,542 branches # 8.947 M/sec ( +- 4.00% ) [83.34%]
> 89,881,640 branch-misses # 0.97% of all branches ( +- 1.17% ) [83.33%]
>
> 18.059261877 seconds time elapsed ( +- 2.65% )
>
> THP on, v3.12-rc2:
> ------------------
>
> Performance counter stats for './thp_memscale -c 80 -b 512m' (5 runs):
>
> 3114745.395974 task-clock # 73.875 CPUs utilized ( +- 1.84% )
> 267,356 context-switches # 0.086 K/sec ( +- 1.84% )
> 99 cpu-migrations # 0.000 K/sec ( +- 1.40% )
> 58,313 page-faults # 0.019 K/sec ( +- 0.28% )
> 7,416,635,817,510 cycles # 2.381 GHz ( +- 1.83% ) [83.33%]
> 7,342,619,196,993 stalled-cycles-frontend # 99.00% frontend cycles idle ( +- 1.88% ) [83.33%]
> 6,267,671,641,967 stalled-cycles-backend # 84.51% backend cycles idle ( +- 2.03% ) [66.67%]
> 117,819,935,165 instructions # 0.02 insns per cycle
> # 62.32 stalled cycles per insn ( +- 4.39% ) [83.34%]
> 28,899,314,777 branches # 9.278 M/sec ( +- 4.48% ) [83.34%]
> 71,787,032 branch-misses # 0.25% of all branches ( +- 1.03% ) [83.33%]
>
> 42.162306788 seconds time elapsed ( +- 1.73% )

THP on, v3.12-rc2:
------------------

Performance counter stats for './thp_memscale -C 0 -m 0 -c 512 -b 512m' (5 runs):

568668865.944994 task-clock # 528.547 CPUs utilized ( +- 0.21% ) [100.00%]
1,491,589 context-switches # 0.000 M/sec ( +- 0.25% ) [100.00%]
1,085 CPU-migrations # 0.000 M/sec ( +- 1.80% ) [100.00%]
400,822 page-faults # 0.000 M/sec ( +- 0.41% )
1,306,612,476,049,478 cycles # 2.298 GHz ( +- 0.23% ) [100.00%]
1,277,211,694,318,724 stalled-cycles-frontend # 97.75% frontend cycles idle ( +- 0.21% ) [100.00%]
1,163,736,844,232,064 stalled-cycles-backend # 89.07% backend cycles idle ( +- 0.20% ) [100.00%]
53,855,178,678,230 instructions # 0.04 insns per cycle
# 23.72 stalled cycles per insn ( +- 1.15% ) [100.00%]
21,041,661,816,782 branches # 37.002 M/sec ( +- 0.64% ) [100.00%]
606,665,092 branch-misses # 0.00% of all branches ( +- 0.63% )

1075.909782795 seconds time elapsed ( +- 0.21% )

> HUGETLB, v3.12-rc2:
> -------------------
>
> Performance counter stats for './thp_memscale_hugetlbfs -c 80 -b 512M' (5 runs):
>
> 2588052.787264 task-clock # 54.400 CPUs utilized ( +- 3.69% )
> 246,831 context-switches # 0.095 K/sec ( +- 4.15% )
> 138 cpu-migrations # 0.000 K/sec ( +- 5.30% )
> 21,027 page-faults # 0.008 K/sec ( +- 0.01% )
> 6,166,666,307,263 cycles # 2.383 GHz ( +- 3.68% ) [83.33%]
> 6,086,008,929,407 stalled-cycles-frontend # 98.69% frontend cycles idle ( +- 3.77% ) [83.33%]
> 5,087,874,435,481 stalled-cycles-backend # 82.51% backend cycles idle ( +- 4.41% ) [66.67%]
> 133,782,831,249 instructions # 0.02 insns per cycle
> # 45.49 stalled cycles per insn ( +- 4.30% ) [83.34%]
> 34,026,870,541 branches # 13.148 M/sec ( +- 4.24% ) [83.34%]
> 68,670,942 branch-misses # 0.20% of all branches ( +- 3.26% ) [83.33%]
>
> 47.574936948 seconds time elapsed ( +- 2.09% )
>
> THP off, patched:
> -----------------
>
> Performance counter stats for './thp_memscale -c 80 -b 512m' (5 runs):
>
> 943301.957892 task-clock # 56.256 CPUs utilized ( +- 3.01% )
> 86,218 context-switches # 0.091 K/sec ( +- 3.17% )
> 121 cpu-migrations # 0.000 K/sec ( +- 6.64% )
> 10,000,551 page-faults # 0.011 M/sec ( +- 0.00% )
> 2,230,462,457,654 cycles # 2.365 GHz ( +- 3.04% ) [83.32%]
> 2,204,616,385,805 stalled-cycles-frontend # 98.84% frontend cycles idle ( +- 3.09% ) [83.32%]
> 1,778,640,046,926 stalled-cycles-backend # 79.74% backend cycles idle ( +- 3.47% ) [66.69%]
> 45,995,472,617 instructions # 0.02 insns per cycle
> # 47.93 stalled cycles per insn ( +- 2.51% ) [83.34%]
> 9,179,700,174 branches # 9.731 M/sec ( +- 3.04% ) [83.35%]
> 89,166,529 branch-misses # 0.97% of all branches ( +- 1.45% ) [83.33%]
>
> 16.768027318 seconds time elapsed ( +- 2.47% )
>
> THP on, patched:
> ----------------
>
> Performance counter stats for './thp_memscale -c 80 -b 512m' (5 runs):
>
> 458793.837905 task-clock # 54.632 CPUs utilized ( +- 0.79% )
> 41,831 context-switches # 0.091 K/sec ( +- 0.97% )
> 98 cpu-migrations # 0.000 K/sec ( +- 1.66% )
> 57,829 page-faults # 0.126 K/sec ( +- 0.62% )
> 1,077,543,336,716 cycles # 2.349 GHz ( +- 0.81% ) [83.33%]
> 1,067,403,802,964 stalled-cycles-frontend # 99.06% frontend cycles idle ( +- 0.87% ) [83.33%]
> 864,764,616,143 stalled-cycles-backend # 80.25% backend cycles idle ( +- 0.73% ) [66.68%]
> 16,129,177,440 instructions # 0.01 insns per cycle
> # 66.18 stalled cycles per insn ( +- 7.94% ) [83.35%]
> 3,618,938,569 branches # 7.888 M/sec ( +- 8.46% ) [83.36%]
> 33,242,032 branch-misses # 0.92% of all branches ( +- 2.02% ) [83.32%]
>
> 8.397885779 seconds time elapsed ( +- 0.18% )

THP on, patched:
----------------

Performance counter stats for './runt -t -c 512 -b 512m' (5 runs):

15836198.490485 task-clock # 533.304 CPUs utilized ( +- 0.95% ) [100.00%]
127,507 context-switches # 0.000 M/sec ( +- 1.65% ) [100.00%]
1,223 CPU-migrations # 0.000 M/sec ( +- 3.23% ) [100.00%]
302,080 page-faults # 0.000 M/sec ( +- 6.88% )
18,925,875,973,975 cycles # 1.195 GHz ( +- 0.43% ) [100.00%]
18,325,469,464,007 stalled-cycles-frontend # 96.83% frontend cycles idle ( +- 0.44% ) [100.00%]
17,522,272,147,141 stalled-cycles-backend # 92.58% backend cycles idle ( +- 0.49% ) [100.00%]
2,686,490,067,197 instructions # 0.14 insns per cycle
# 6.82 stalled cycles per insn ( +- 2.16% ) [100.00%]
944,712,646,402 branches # 59.655 M/sec ( +- 2.03% ) [100.00%]
145,956,565 branch-misses # 0.02% of all branches ( +- 0.88% )

29.694499652 seconds time elapsed ( +- 0.95% )

(these results are from the test suite that I ripped thp_memscale out
of, but it's the same test)

> HUGETLB, patched
> -----------------
>
> Performance counter stats for './thp_memscale_hugetlbfs -c 80 -b 512M' (5 runs):
>
> 395353.076837 task-clock # 20.329 CPUs utilized ( +- 8.16% )
> 55,730 context-switches # 0.141 K/sec ( +- 5.31% )
> 138 cpu-migrations # 0.000 K/sec ( +- 4.24% )
> 21,027 page-faults # 0.053 K/sec ( +- 0.00% )
> 930,219,717,244 cycles # 2.353 GHz ( +- 8.21% ) [83.32%]
> 914,295,694,103 stalled-cycles-frontend # 98.29% frontend cycles idle ( +- 8.35% ) [83.33%]
> 704,137,950,187 stalled-cycles-backend # 75.70% backend cycles idle ( +- 9.16% ) [66.69%]
> 30,541,538,385 instructions # 0.03 insns per cycle
> # 29.94 stalled cycles per insn ( +- 3.98% ) [83.35%]
> 8,415,376,631 branches # 21.286 M/sec ( +- 3.61% ) [83.36%]
> 32,645,478 branch-misses # 0.39% of all branches ( +- 3.41% ) [83.32%]
>
> 19.447481153 seconds time elapsed ( +- 2.00% )
>
> Kirill A. Shutemov (10):
> mm: rename USE_SPLIT_PTLOCKS to USE_SPLIT_PTE_PTLOCKS
> mm: convert mm->nr_ptes to atomic_t
> mm: introduce api for split page table lock for PMD level
> mm, thp: change pmd_trans_huge_lock() to return taken lock
> mm, thp: move ptl taking inside page_check_address_pmd()
> mm, thp: do not access mm->pmd_huge_pte directly
> mm, hugetlb: convert hugetlbfs to use split pmd lock
> mm: convent the rest to new page table lock api
> mm: implement split page table lock for PMD level
> x86, mm: enable split page table lock for PMD level
>
> arch/arm/mm/fault-armv.c | 6 +-
> arch/s390/mm/pgtable.c | 12 +--
> arch/sparc/mm/tlb.c | 12 +--
> arch/x86/Kconfig | 4 +
> arch/x86/include/asm/pgalloc.h | 11 ++-
> arch/x86/xen/mmu.c | 6 +-
> fs/proc/meminfo.c | 2 +-
> fs/proc/task_mmu.c | 16 ++--
> include/linux/huge_mm.h | 17 ++--
> include/linux/hugetlb.h | 25 +++++
> include/linux/mm.h | 52 ++++++++++-
> include/linux/mm_types.h | 18 ++--
> include/linux/swapops.h | 7 +-
> kernel/fork.c | 6 +-
> mm/Kconfig | 3 +
> mm/huge_memory.c | 201 ++++++++++++++++++++++++-----------------
> mm/hugetlb.c | 108 +++++++++++++---------
> mm/memcontrol.c | 10 +-
> mm/memory.c | 21 +++--
> mm/mempolicy.c | 5 +-
> mm/migrate.c | 14 +--
> mm/mmap.c | 3 +-
> mm/mprotect.c | 4 +-
> mm/oom_kill.c | 6 +-
> mm/pgtable-generic.c | 16 ++--
> mm/rmap.c | 15 ++-
> 26 files changed, 379 insertions(+), 221 deletions(-)
>
> --
> 1.8.4.rc3
>
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