Messages in this thread | | | Date | Tue, 23 Aug 2022 11:45:34 +0800 | From | Chen Yu <> | Subject | Re: [PATCH v7 2/2] sched/fair: Scan cluster before scanning LLC in wake-up path |
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On 2022-08-22 at 15:36:10 +0800, Yicong Yang wrote: > From: Barry Song <song.bao.hua@hisilicon.com> > > For platforms having clusters like Kunpeng920, CPUs within the same cluster > have lower latency when synchronizing and accessing shared resources like > cache. Thus, this patch tries to find an idle cpu within the cluster of the > target CPU before scanning the whole LLC to gain lower latency. > > Testing has been done on Kunpeng920 by pinning tasks to one numa and two > numa. On Kunpeng920, Each numa has 8 clusters and each cluster has 4 CPUs. > > With this patch, We noticed enhancement on tbench within one numa or cross > two numa. > > On numa 0: > 6.0-rc1 patched > Hmean 1 351.20 ( 0.00%) 396.45 * 12.88%* > Hmean 2 700.43 ( 0.00%) 793.76 * 13.32%* > Hmean 4 1404.42 ( 0.00%) 1583.62 * 12.76%* > Hmean 8 2833.31 ( 0.00%) 3147.85 * 11.10%* > Hmean 16 5501.90 ( 0.00%) 6089.89 * 10.69%* > Hmean 32 10428.59 ( 0.00%) 10619.63 * 1.83%* > Hmean 64 8223.39 ( 0.00%) 8306.93 * 1.02%* > Hmean 128 7042.88 ( 0.00%) 7068.03 * 0.36%* > > On numa 0-1: > 6.0-rc1 patched > Hmean 1 363.06 ( 0.00%) 397.13 * 9.38%* > Hmean 2 721.68 ( 0.00%) 789.84 * 9.44%* > Hmean 4 1435.15 ( 0.00%) 1566.01 * 9.12%* > Hmean 8 2776.17 ( 0.00%) 3007.05 * 8.32%* > Hmean 16 5471.71 ( 0.00%) 6103.91 * 11.55%* > Hmean 32 10164.98 ( 0.00%) 11531.81 * 13.45%* > Hmean 64 17143.28 ( 0.00%) 20078.68 * 17.12%* > Hmean 128 14552.70 ( 0.00%) 15156.41 * 4.15%* > Hmean 256 12827.37 ( 0.00%) 13326.86 * 3.89%* > > Note neither Kunpeng920 nor x86 Jacobsville supports SMT, so the SMT branch > in the code has not been tested but it supposed to work. > > Suggested-by: Peter Zijlstra <peterz@infradead.org> > [https://lore.kernel.org/lkml/Ytfjs+m1kUs0ScSn@worktop.programming.kicks-ass.net] > Tested-by: Yicong Yang <yangyicong@hisilicon.com> > Signed-off-by: Barry Song <song.bao.hua@hisilicon.com> > Signed-off-by: Yicong Yang <yangyicong@hisilicon.com> > Reviewed-by: Tim Chen <tim.c.chen@linux.intel.com> > --- > kernel/sched/fair.c | 30 +++++++++++++++++++++++++++--- > kernel/sched/sched.h | 2 ++ > kernel/sched/topology.c | 10 ++++++++++ > 3 files changed, 39 insertions(+), 3 deletions(-) > > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c > index 914096c5b1ae..6fa77610d0f5 100644 > --- a/kernel/sched/fair.c > +++ b/kernel/sched/fair.c > @@ -6437,6 +6437,30 @@ static int select_idle_cpu(struct task_struct *p, struct sched_domain *sd, bool > } > } > > + if (static_branch_unlikely(&sched_cluster_active)) { > + struct sched_domain *sdc = rcu_dereference(per_cpu(sd_cluster, target)); > + > + if (sdc) { > + for_each_cpu_wrap(cpu, sched_domain_span(sdc), target + 1) { Looks good to me. One minor question, why don't we use cpumask_and(cpus, sched_domain_span(sdc), cpus); > + if (!cpumask_test_cpu(cpu, cpus)) > + continue; so above check can be removed in each loop? Besides may I know what version this patch is based on? since I failed to apply the patch on v6.0-rc2. Other than that:
Reviewed-by: Chen Yu <yu.c.chen@intel.com>
thanks, Chenyu > + > + if (has_idle_core) { > + i = select_idle_core(p, cpu, cpus, &idle_cpu); > + if ((unsigned int)i < nr_cpumask_bits) > + return i; > + } else { > + if (--nr <= 0) > + return -1; > + idle_cpu = __select_idle_cpu(cpu, p); > + if ((unsigned int)idle_cpu < nr_cpumask_bits) > + return idle_cpu; > + } > + } > + cpumask_andnot(cpus, cpus, sched_domain_span(sdc)); > + } > + }
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