From: Parth Shah <parth@linux.ibm.com>
To: subhra mazumdar <subhra.mazumdar@oracle.com>,
linux-kernel@vger.kernel.org
Cc: peterz@infradead.org, mingo@redhat.com, tglx@linutronix.de,
steven.sistare@oracle.com, dhaval.giani@oracle.com,
daniel.lezcano@linaro.org, vincent.guittot@linaro.org,
viresh.kumar@linaro.org, tim.c.chen@linux.intel.com,
mgorman@techsingularity.net, patrick.bellasi@arm.com
Subject: Re: [RFC PATCH 2/9] sched: add search limit as per latency-nice
Date: Thu, 5 Sep 2019 11:52:06 +0530 [thread overview]
Message-ID: <5b7d3790-2510-f8b1-6515-bb9d307bba25@linux.ibm.com> (raw)
In-Reply-To: <20190830174944.21741-3-subhra.mazumdar@oracle.com>
On 8/30/19 11:19 PM, subhra mazumdar wrote:
> Put upper and lower limit on CPU search in select_idle_cpu. The lower limit
> is set to amount of CPUs in a core while upper limit is derived from the
> latency-nice of the thread. This ensures for any architecture we will
> usually search beyond a core. Changing the latency-nice value by user will
> change the search cost making it appropriate for given workload.
>
> Signed-off-by: subhra mazumdar <subhra.mazumdar@oracle.com>
> ---
> kernel/sched/fair.c | 13 +++++++------
> 1 file changed, 7 insertions(+), 6 deletions(-)
>
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index b08d00c..c31082d 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -6188,7 +6188,7 @@ static int select_idle_cpu(struct task_struct *p, struct sched_domain *sd, int t
> u64 avg_cost, avg_idle;
> u64 time, cost;
> s64 delta;
> - int cpu, nr = INT_MAX;
> + int cpu, floor, nr = INT_MAX;
>
> this_sd = rcu_dereference(*this_cpu_ptr(&sd_llc));
> if (!this_sd)
> @@ -6205,11 +6205,12 @@ static int select_idle_cpu(struct task_struct *p, struct sched_domain *sd, int t
> return -1;
>
> if (sched_feat(SIS_PROP)) {
> - u64 span_avg = sd->span_weight * avg_idle;
> - if (span_avg > 4*avg_cost)
> - nr = div_u64(span_avg, avg_cost);
> - else
> - nr = 4;
> + floor = cpumask_weight(topology_sibling_cpumask(target));
> + if (floor < 2)
> + floor = 2;
> + nr = (p->latency_nice * sd->span_weight) / LATENCY_NICE_MAX;
I see you defined LATENCY_NICE_MAX = 100,
So is the value 100 an experimental value?
I was hoping to be something in the power of 2 resulting in just ">>>" rather than
the heavy division operation.
> + if (nr < floor)
> + nr = floor;
> }
>
> time = local_clock();
>
next prev parent reply other threads:[~2019-09-05 6:22 UTC|newest]
Thread overview: 55+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-30 17:49 [RFC PATCH 0/9] Task latency-nice subhra mazumdar
2019-08-30 17:49 ` [RFC PATCH 1/9] sched,cgroup: Add interface for latency-nice subhra mazumdar
2019-09-04 17:32 ` Tim Chen
2019-09-05 6:15 ` Parth Shah
2019-09-05 10:11 ` Patrick Bellasi
2019-09-06 12:22 ` Parth Shah
2019-09-05 8:31 ` Peter Zijlstra
2019-09-05 9:45 ` Patrick Bellasi
2019-09-05 10:46 ` Peter Zijlstra
2019-09-05 11:13 ` Qais Yousef
2019-09-05 11:30 ` Peter Zijlstra
2019-09-05 11:40 ` Patrick Bellasi
2019-09-05 11:48 ` Peter Zijlstra
2019-09-05 13:32 ` Qais Yousef
2019-09-05 11:47 ` Qais Yousef
2020-04-16 0:02 ` Joel Fernandes
2020-04-16 17:23 ` Dietmar Eggemann
2020-04-18 16:01 ` Joel Fernandes
2020-04-20 11:26 ` Parth Shah
2020-04-20 19:14 ` Joel Fernandes
2020-04-20 11:47 ` Qais Yousef
2020-04-20 19:10 ` Joel Fernandes
2019-09-05 11:30 ` Patrick Bellasi
2019-09-05 11:47 ` Peter Zijlstra
2019-09-05 11:18 ` Patrick Bellasi
2019-09-05 11:40 ` Peter Zijlstra
2019-09-05 11:46 ` Patrick Bellasi
2019-09-05 11:46 ` Valentin Schneider
2019-09-05 13:07 ` Patrick Bellasi
2019-09-05 14:48 ` Valentin Schneider
2019-09-06 12:45 ` Parth Shah
2019-09-06 14:13 ` Valentin Schneider
2019-09-06 14:32 ` Vincent Guittot
2019-09-06 17:10 ` Parth Shah
2019-09-06 22:50 ` Valentin Schneider
2019-09-06 12:31 ` Parth Shah
2019-09-05 10:05 ` Patrick Bellasi
2019-09-05 10:48 ` Peter Zijlstra
2019-08-30 17:49 ` [RFC PATCH 2/9] sched: add search limit as per latency-nice subhra mazumdar
2019-09-05 6:22 ` Parth Shah [this message]
2019-08-30 17:49 ` [RFC PATCH 3/9] sched: add sched feature to disable idle core search subhra mazumdar
2019-09-05 10:17 ` Patrick Bellasi
2019-09-05 22:02 ` Subhra Mazumdar
2019-08-30 17:49 ` [RFC PATCH 4/9] sched: SIS_CORE " subhra mazumdar
2019-09-05 10:19 ` Patrick Bellasi
2019-08-30 17:49 ` [RFC PATCH 5/9] sched: Define macro for number of CPUs in core subhra mazumdar
2019-08-30 17:49 ` [RFC PATCH 6/9] x86/smpboot: Optimize cpumask_weight_sibling macro for x86 subhra mazumdar
2019-08-30 17:49 ` [RFC PATCH 7/9] sched: search SMT before LLC domain subhra mazumdar
2019-09-05 9:31 ` Peter Zijlstra
2019-09-05 20:40 ` Subhra Mazumdar
2019-08-30 17:49 ` [RFC PATCH 8/9] sched: introduce per-cpu var next_cpu to track search limit subhra mazumdar
2019-08-30 17:49 ` [RFC PATCH 9/9] sched: rotate the cpu search window for better spread subhra mazumdar
2019-09-05 6:37 ` Parth Shah
2019-09-05 5:55 ` [RFC PATCH 0/9] Task latency-nice Parth Shah
2019-09-05 10:31 ` Patrick Bellasi
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