On Fri, Jan 10, 2014 at 01:55:18PM -0600, Alex Thorlton wrote: > This patch adds an mm flag (MMF_THP_DISABLE) to disable transparent > hugepages using prctl. It is based on my original patch to add a > per-task_struct flag to disable THP: > > v1 - https://lkml.org/lkml/2013/8/2/671 > v2 - https://lkml.org/lkml/2013/8/2/703 > > After looking at alternate methods of modifying how THPs are handed out, > it sounds like people might be more in favor of this type of approach, > so I'm re-introducing the patch. > > It seemed that everyone was in favor of moving this control over to the > mm_struct, if it is to be implemented. That's the only major change > here, aside from the added ability to both set and clear the flag from > prctl. > > The main motivation behind this patch is to provide a way to disable THP > for jobs where the code cannot be modified and using a malloc hook with > madvise is not an option (i.e. statically allocated data). This patch > allows us to do just that, without affecting other jobs running on the > system. > > Here are some results showing the improvement that my test case gets > when the MMF_THP_DISABLE flag is clear vs. set: > > MMF_THP_DISABLE clear: > > # perf stat -a -r 3 ./prctl_wrapper_mm 0 ./thp_pthread -C 0 -m 0 -c 512 -b > 256g > > Performance counter stats for './prctl_wrapper_mm 0 ./thp_pthread -C 0 -m 0 > -c 512 -b 256g' (3 runs): > > 267694862.049279 task-clock # 641.100 CPUs utilized > ( +- 0.23% ) [100.00%] > 908,846 context-switches # 0.000 M/sec > ( +- 0.23% ) [100.00%] > 874 CPU-migrations # 0.000 M/sec > ( +- 4.01% ) [100.00%] > 131,966 page-faults # 0.000 M/sec > ( +- 2.75% ) > 351,127,909,744,906 cycles # 1.312 GHz > ( +- 0.27% ) [100.00%] > 523,537,415,562,692 stalled-cycles-frontend # 149.10% frontend cycles idle > ( +- 0.26% ) [100.00%] > 392,400,753,609,156 stalled-cycles-backend # 111.75% backend cycles idle > ( +- 0.29% ) [100.00%] > 147,467,956,557,895 instructions # 0.42 insns per cycle > # 3.55 stalled cycles per > insn ( +- 0.09% ) [100.00%] > 26,922,737,309,021 branches # 100.572 M/sec > ( +- 0.24% ) [100.00%] > 1,308,714,545 branch-misses # 0.00% of all branches > ( +- 0.18% ) > > 417.555688399 seconds time elapsed > ( +- 0.23% ) > > > MMF_THP_DISABLE set: > > # perf stat -a -r 3 ./prctl_wrapper_mm 1 ./thp_pthread -C 0 -m 0 -c 512 -b > 256g > > Performance counter stats for './prctl_wrapper_mm 1 ./thp_pthread -C 0 -m 0 > -c 512 -b 256g' (3 runs): > > 141674994.160138 task-clock # 642.107 CPUs utilized > ( +- 0.23% ) [100.00%] > 1,190,415 context-switches # 0.000 M/sec > ( +- 42.87% ) [100.00%] > 688 CPU-migrations # 0.000 M/sec > ( +- 2.47% ) [100.00%] > 62,394,646 page-faults # 0.000 M/sec > ( +- 0.00% ) > 156,748,225,096,919 cycles # 1.106 GHz > ( +- 0.20% ) [100.00%] > 211,440,354,290,433 stalled-cycles-frontend # 134.89% frontend cycles idle > ( +- 0.40% ) [100.00%] > 114,304,536,881,102 stalled-cycles-backend # 72.92% backend cycles idle > ( +- 0.88% ) [100.00%] > 179,939,084,230,732 instructions # 1.15 insns per cycle > # 1.18 stalled cycles per > insn ( +- 0.26% ) [100.00%] > 26,659,099,949,509 branches # 188.171 M/sec > ( +- 0.72% ) [100.00%] > 762,772,361 branch-misses # 0.00% of all branches > ( +- 0.97% ) > > 220.640905073 seconds time elapsed > ( +- 0.23% ) > > As you can see, this particular test gets about a 2x performance boost > when THP is turned off.
Do you know what cause the difference? I prefer to fix THP instead of adding new knob to disable it. -- Kirill A. Shutemov -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
