> 2012/7/4 Pekka Enberg <penberg@xxxxxxxxxx>: >> 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. On Wed, Jul 4, 2012 at 5:30 PM, JoonSoo Kim <js1304@xxxxxxxxx> wrote: > 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. Prefetching can also have negative effect on overall performance: http://lwn.net/Articles/444336/ > 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% ) That doesn't seem like that obvious win to me... Eric, Christoph? -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>