On Fri, Jun 14, 2013 at 10:35:22PM -0700, Tejun Heo wrote: > On Fri, Jun 14, 2013 at 03:31:25PM -0700, Tejun Heo wrote: > > I'll play with it a bit more on an actual machine and post more > > results. Test program attached. > > So, here are the results from the same test on a dual-socket 2-way > NUMA opteron 8 core machine. > > Running on one CPU. > > copy size atomic percpu diff in pct > 0 535964443 616756827 +15.07% > 32 399988186 378678713 -5.33% > 64 389067476 355073979 -8.74% > 128 342192631 315615300 -7.77% > 256 281208005 260598931 -7.33% > 512 188070912 193225269 +2.74% > > Running on all eight cores. > > copy size atomic percpu diff in pct > 0 121324328 4889425511 +3,930.05% > 32 96170193 2999613380 +3,019.07% > 64 98139061 2813894184 +2,767.25% > 128 112610025 2503229487 +2,122.92% > 256 96828114 2069865752 +2,037.67% > 512 95858297 1537726109 +1,504.17% > > Ration of all cores / single core. > > copy size atomic percpu > 0 0.23 7.93 > 32 0.24 7.92 > 64 0.25 7.92 > 128 0.33 7.93 > 256 0.34 7.94 > 512 0.51 7.96
I was testing with CONFIG_PREEMPT, which makes rcu_read_[un]lock()s quite a bit more expensive. The following is the same test results with CONFIG_PREEMPT_VOLUNTARY which would the most preemptive server distros would get anyway. One CPU. copy size atomic percpu diff in pct 0 534583387 1521561724 +184.63% 32 399098138 615962137 + 54.34% 64 388128431 555599274 + 43.15% 128 341336474 464502792 + 36.08% 256 280471681 354186740 + 26.28% 512 203784802 240067596 + 17.80% All eight CPUs. copy size atomic percpu diff in pct 0 117213982 12488998111 +10,554.87% 32 103545751 4940695158 + 4,671.51% 64 98135094 4456370409 + 4,441.06% 128 117729659 3725434154 + 3,064.40% 256 95916768 2840992396 + 2,861.94% 512 95795993 1926044518 + 1,910.57% Ration of all cores / single core. copy size atomic percpu 0 0.22 8.21 32 0.26 8.02 64 0.25 8.02 128 0.34 8.02 256 0.34 8.02 512 0.47 8.02 So, it's faster even with only one CPU. Thanks. -- tejun -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
