On Thu, Mar 05, 2015 at 11:54:52PM +0000, Mel Gorman wrote: > Dave Chinner reported the following on https://lkml.org/lkml/2015/3/1/226 > > Across the board the 4.0-rc1 numbers are much slower, and the > degradation is far worse when using the large memory footprint > configs. Perf points straight at the cause - this is from 4.0-rc1 > on the "-o bhash=101073" config: > > - 56.07% 56.07% [kernel] [k] default_send_IPI_mask_sequence_phys > - default_send_IPI_mask_sequence_phys > - 99.99% physflat_send_IPI_mask > - 99.37% native_send_call_func_ipi > smp_call_function_many > - native_flush_tlb_others > - 99.85% flush_tlb_page > ptep_clear_flush > try_to_unmap_one > rmap_walk > try_to_unmap > migrate_pages > migrate_misplaced_page > - handle_mm_fault > - 99.73% __do_page_fault > trace_do_page_fault > do_async_page_fault > + async_page_fault > 0.63% native_send_call_func_single_ipi > generic_exec_single > smp_call_function_single > > This was bisected to commit 4d9424669946 ("mm: convert p[te|md]_mknonnuma > and remaining page table manipulations") which clears PTEs and PMDs to make > them PROT_NONE. This is tidy but tests on some benchmarks indicate that > there are many more hinting faults trapped resulting in excessive migration. > This is the result for the old autonuma benchmark for example. [snip] Doesn't fix the problem. Runtime is slightly improved (16m45s vs 17m35) but it's still much slower that 3.19 (6m5s). Stats and profiles still roughly the same: 360,228 migrate:mm_migrate_pages ( +- 4.28% ) - 52.69% 52.69% [kernel] [k] default_send_IPI_mask_sequence_phys default_send_IPI_mask_sequence_phys - physflat_send_IPI_mask - 97.28% native_send_call_func_ipi smp_call_function_many native_flush_tlb_others flush_tlb_page ptep_clear_flush try_to_unmap_one rmap_walk try_to_unmap migrate_pages migrate_misplaced_page - handle_mm_fault - 99.59% __do_page_fault trace_do_page_fault do_async_page_fault + async_page_fault + 2.72% native_send_call_func_single_ipi numa_hit 36678767 numa_miss 905234 numa_foreign 905234 numa_interleave 14802 numa_local 36656791 numa_other 927210 numa_pte_updates 92168450 numa_huge_pte_updates 0 numa_hint_faults 87573926 numa_hint_faults_local 29730293 numa_pages_migrated 30195890 pgmigrate_success 30195890 pgmigrate_fail 0 Cheers, Dave. -- Dave Chinner david@xxxxxxxxxxxxx -- 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>