Messages in this thread | | | Date | Wed, 4 Jul 2012 23:30:14 +0900 | Subject | Re: [PATCH 1/3 v2] slub: prefetch next freelist pointer in __slab_alloc() | From | JoonSoo Kim <> |
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2012/7/4 Pekka Enberg <penberg@kernel.org>: > Well, can you show improvement in any benchmark or workload? > Prefetching is not always an obvious win and the reason we merged > Eric's patch was that he was able to show an improvement in hackbench.
I thinks that this patch is perfectly same effect as Eric's patch, so doesn't include benchmark result. Eric's patch which add "prefetch instruction" in fastpath works for second ~ last object of cpu slab. This patch which add "prefetch instrunction" in slowpath works for first object of cpu slab.
But, I do test "./perf stat -r 20 ./hackbench 50 process 4000 > /dev/null" and gain following outputs.
***** vanilla *****
Performance counter stats for './hackbench 50 process 4000' (20 runs):
114189.571311 task-clock # 7.924 CPUs utilized ( +- 0.29% ) 2,978,515 context-switches # 0.026 M/sec ( +- 3.45% ) 102,635 CPU-migrations # 0.899 K/sec ( +- 5.63% ) 123,948 page-faults # 0.001 M/sec ( +- 0.16% ) 422,477,120,134 cycles # 3.700 GHz ( +- 0.29% ) <not supported> stalled-cycles-frontend <not supported> stalled-cycles-backend 251,943,851,074 instructions # 0.60 insns per cycle ( +- 0.14% ) 46,214,207,979 branches # 404.715 M/sec ( +- 0.15% ) 215,342,095 branch-misses # 0.47% of all branches ( +- 0.53% )
14.409990448 seconds time elapsed ( +- 0.30% )
Performance counter stats for './hackbench 50 process 4000' (20 runs):
114576.053284 task-clock # 7.921 CPUs utilized ( +- 0.35% ) 2,810,138 context-switches # 0.025 M/sec ( +- 3.21% ) 85,641 CPU-migrations # 0.747 K/sec ( +- 5.05% ) 124,299 page-faults # 0.001 M/sec ( +- 0.18% ) 423,906,539,517 cycles # 3.700 GHz ( +- 0.35% ) <not supported> stalled-cycles-frontend <not supported> stalled-cycles-backend 251,354,351,283 instructions # 0.59 insns per cycle ( +- 0.13% ) 46,098,601,012 branches # 402.341 M/sec ( +- 0.13% ) 213,448,657 branch-misses # 0.46% of all branches ( +- 0.50% )
14.464325969 seconds time elapsed ( +- 0.34% )
***** patch applied *****
Performance counter stats for './hackbench 50 process 4000' (20 runs):
112935.199731 task-clock # 7.926 CPUs utilized ( +- 0.29% ) 2,810,157 context-switches # 0.025 M/sec ( +- 2.95% ) 104,278 CPU-migrations # 0.923 K/sec ( +- 6.83% ) 123,999 page-faults # 0.001 M/sec ( +- 0.17% ) 417,834,406,420 cycles # 3.700 GHz ( +- 0.29% ) <not supported> stalled-cycles-frontend <not supported> stalled-cycles-backend 251,291,523,926 instructions # 0.60 insns per cycle ( +- 0.11% ) 46,083,091,476 branches # 408.049 M/sec ( +- 0.12% ) 213,714,228 branch-misses # 0.46% of all branches ( +- 0.43% )
14.248980376 seconds time elapsed ( +- 0.29% )
Performance counter stats for './hackbench 50 process 4000' (20 runs):
113640.944855 task-clock # 7.926 CPUs utilized ( +- 0.28% ) 2,776,983 context-switches # 0.024 M/sec ( +- 5.66% ) 95,962 CPU-migrations # 0.844 K/sec ( +- 10.69% ) 123,849 page-faults # 0.001 M/sec ( +- 0.15% ) 420,446,572,595 cycles # 3.700 GHz ( +- 0.28% ) <not supported> stalled-cycles-frontend <not supported> stalled-cycles-backend 251,174,259,429 instructions # 0.60 insns per cycle ( +- 0.21% ) 46,060,683,039 branches # 405.318 M/sec ( +- 0.23% ) 213,480,999 branch-misses # 0.46% of all branches ( +- 0.75% )
14.336843534 seconds time elapsed ( +- 0.28% )
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