On Tue, Jun 04, 2013 at 04:57:57PM +0800, Jianguo Wu wrote:
>Hi all,
>
>I tested memcpy with perf bench, and found that in prefault case, When Transparent Hugepage is on,
>memcpy has worse performance.
>
>When THP on is 3.672879 GB/Sec (with prefault), while THP off is 6.190187 GB/Sec (with prefault).
>
I get similar result as you against 3.10-rc4 in the attachment. This
dues to the characteristic of thp takes a single page fault for each
2MB virtual region touched by userland.
>I think THP will improve performance, but the test result obviously not the case.
>Andrea mentioned THP cause "clear_page/copy_page less cache friendly" in
>http://events.linuxfoundation.org/slides/2011/lfcs/lfcs2011_hpc_arcangeli.pdf.
>
>I am not quite understand this, could you please give me some comments, Thanks!
>
>I test in Linux-3.4-stable, and my machine info is:
>Intel(R) Xeon(R) CPU E5520 @ 2.27GHz
>
>available: 2 nodes (0-1)
>node 0 cpus: 0 1 2 3 8 9 10 11
>node 0 size: 24567 MB
>node 0 free: 23550 MB
>node 1 cpus: 4 5 6 7 12 13 14 15
>node 1 size: 24576 MB
>node 1 free: 23767 MB
>node distances:
>node 0 1
> 0: 10 20
> 1: 20 10
>
>Below is test result:
>---with THP---
>#cat /sys/kernel/mm/transparent_hugepage/enabled
>[always] madvise never
>#./perf bench mem memcpy -l 1gb -o
># Running mem/memcpy benchmark...
># Copying 1gb Bytes ...
>
> 3.672879 GB/Sec (with prefault)
>
>#./perf stat ...
>Performance counter stats for './perf bench mem memcpy -l 1gb -o':
>
> 35455940 cache-misses # 53.504 % of all cache refs [49.45%]
> 66267785 cache-references [49.78%]
> 2409 page-faults
> 450768651 dTLB-loads
> [50.78%]
> 24580 dTLB-misses
> # 0.01% of all dTLB cache hits [51.01%]
> 1338974202 dTLB-stores
> [50.63%]
> 77943 dTLB-misses
> [50.24%]
> 697404997 iTLB-loads
> [49.77%]
> 274 iTLB-misses
> # 0.00% of all iTLB cache hits [49.30%]
>
> 0.855041819 seconds time elapsed
>
>---no THP---
>#cat /sys/kernel/mm/transparent_hugepage/enabled
>always madvise [never]
>
>#./perf bench mem memcpy -l 1gb -o
># Running mem/memcpy benchmark...
># Copying 1gb Bytes ...
>
> 6.190187 GB/Sec (with prefault)
>
>#./perf stat ...
>Performance counter stats for './perf bench mem memcpy -l 1gb -o':
>
> 16920763 cache-misses # 98.377 % of all cache refs [50.01%]
> 17200000 cache-references [50.04%]
> 524652 page-faults
> 734365659 dTLB-loads
> [50.04%]
> 4986387 dTLB-misses
> # 0.68% of all dTLB cache hits [50.04%]
> 1013408298 dTLB-stores
> [50.04%]
> 8180817 dTLB-misses
> [49.97%]
> 1526642351 iTLB-loads
> [50.41%]
> 56 iTLB-misses
> # 0.00% of all iTLB cache hits [50.21%]
>
> 1.025425847 seconds time elapsed
>
>Thanks,
>Jianguo Wu.
>
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---with THP---
#cat /sys/kernel/mm/transparent_hugepage/enabled
[always] madvise never
# Running mem/memcpy benchmark...
# Copying 1gb Bytes ...
12.208522 GB/Sec (with prefault)
Performance counter stats for './perf bench mem memcpy -l 1gb -o':
26,453,696 cache-misses # 35.411 % of all cache refs [57.66%]
74,704,531 cache-references [58.40%]
2,297 page-faults
146,567,960 dTLB-loads [58.64%]
211,648,685 dTLB-stores [58.63%]
14,533 dTLB-load-misses # 0.01% of all dTLB cache hits [57.46%]
640 iTLB-loads [55.74%]
270,881 iTLB-load-misses # 42325.16% of all iTLB cache hits [55.17%]
0.232425109 seconds time elapsed
---no THP---
#cat /sys/kernel/mm/transparent_hugepage/enabled
always madvise [never]
# Running mem/memcpy benchmark...
# Copying 1gb Bytes ...
18.325087 GB/Sec (with prefault)
Performance counter stats for './perf bench mem memcpy -l 1gb -o':
28,498,544 cache-misses # 86.167 % of all cache refs [57.35%]
33,073,611 cache-references [57.71%]
524,540 page-faults
453,500,641 dTLB-loads [57.99%]
409,255,606 dTLB-stores [57.99%]
2,033,985 dTLB-load-misses # 0.45% of all dTLB cache hits [57.52%]
1,180 iTLB-loads [56.69%]
539,056 iTLB-load-misses # 45682.71% of all iTLB cache hits [56.02%]
0.485932214 seconds time elapsed