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Date: Sat, 30 Jan 2016 18:53:05 +0100 From: Mike Galbraith <umgwanakikbuti@...il.com> To: Frederic Weisbecker <fweisbec@...il.com>, Rik van Riel <riel@...hat.com> Cc: linux-kernel@...r.kernel.org, tglx@...utronix.de, mingo@...nel.org, peterz@...radead.org, luto@...capital.net, Clark Williams <williams@...hat.com> Subject: Re: [PATCH 2/2] sched,time: call __acct_update_integrals once a jiffy On Sat, 2016-01-30 at 15:20 +0100, Frederic Weisbecker wrote: > On Fri, Jan 29, 2016 at 05:43:28PM -0500, Rik van Riel wrote: > > Run times for the microbenchmark: > > > > 4.4 3.8 seconds > > 4.5-rc1 3.7 seconds > > 4.5-rc1 + first patch 3.3 seconds > > 4.5-rc1 + both patches 2.3 seconds > > Very nice improvement! Tasty indeed. When nohz_full CPUs are not isolated, ie are being used as generic CPUs, get_nohz_timer_target() is a problem with things like tbench. tbench 8 with Rik's patches applied: nohz_full=empty Throughput 3204.69 MB/sec 1.000 nohz_full=1-3,5-7 Throughput 1354.99 MB/sec .422 1.000 nohz_full=1-3,5-7 + club below Throughput 2762.22 MB/sec .861 2.038 With Rik's patches and a club, tbench becomes nearly acceptable. --- include/linux/tick.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/include/linux/tick.h +++ b/include/linux/tick.h @@ -184,7 +184,7 @@ static inline const struct cpumask *hous static inline bool is_housekeeping_cpu(int cpu) { #ifdef CONFIG_NO_HZ_FULL - if (tick_nohz_full_enabled()) + if (tick_nohz_full_enabled() && runqueue_is_isolated(cpu)) return cpumask_test_cpu(cpu, housekeeping_mask); #endif return true;
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