From: "Ofer Levi(SW)" <oferle@mellanox.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: "rusty@rustcorp.com.au" <rusty@rustcorp.com.au>,
"mingo@redhat.com" <mingo@redhat.com>,
"Vineet.Gupta1@synopsys.com" <Vineet.Gupta1@synopsys.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Tejun Heo <tj@kernel.org>
Subject: RE: hotplug support for arch/arc/plat-eznps platform
Date: Thu, 10 Aug 2017 07:40:16 +0000 [thread overview]
Message-ID: <VI1PR0501MB2110C116B9791B98D2E0C0ECB2880@VI1PR0501MB2110.eurprd05.prod.outlook.com> (raw)
In-Reply-To: <20170809153437.gngof7hiiny2zv3j@hirez.programming.kicks-ass.net>
Well, this definitely have pleased the little toy :)
Thank you. I really appreciate your time and effort.
If I may, one more newbie question. What do I need to do for the two patches to find
their way into formal kernel code?
Thanks
-Ofer
> -----Original Message-----
> From: Peter Zijlstra [mailto:peterz@infradead.org]
> Sent: Wednesday, August 9, 2017 6:35 PM
> To: Ofer Levi(SW) <oferle@mellanox.com>
> Cc: rusty@rustcorp.com.au; mingo@redhat.com;
> Vineet.Gupta1@synopsys.com; linux-kernel@vger.kernel.org; Tejun Heo
> <tj@kernel.org>
> Subject: Re: hotplug support for arch/arc/plat-eznps platform
>
> On Wed, Aug 09, 2017 at 03:19:02PM +0000, Ofer Levi(SW) wrote:
> > I appreciate your effort and detailed reply, however I'm still
> > experiencing performance hit at partition_sched_domains(). It seems the
> issue is due to the large magnitude of cpus.
> > I used he suggested method 2, patched in the diffs and used the
> > command line switch isolcpus to kill load-balancing.
> > It did save few hundredth of a sec per cpu. When I limited number of
> > available cpus (using present and possible cpus ) to 48, it did reduced
> dramatically this function execution time:
> >
> > With 4K available cpus :
> > [ 48.890000] ## CPU16 LIVE ##: Executing Code...
> > [ 48.910000] partition_sched_domains start
> > [ 49.360000] partition_sched_domains end
> >
> > With 48 available cpus:
> > [ 36.950000] ## CPU16 LIVE ##: Executing Code...
> > [ 36.950000] partition_sched_domains start
> > [ 36.960000] partition_sched_domains end
> >
> > Note that I currently use kernel version: 4.8.0.17.0600.00.0000, if this has
> any influence.
> > Would appreciate your thoughts.
> >
>
> Does something like this cure things? It seems we're doing a possible_cpus
> iteration for sysctl cruft, and that will most certainly hurt on your little toy :-)
>
> Not sure what the more generic solution to that would be, but the below
> avoids it for isolcpus.
>
> ---
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -85,6 +85,7 @@ int sysctl_sched_rt_runtime = 950000;
>
> /* CPUs with isolated domains */
> cpumask_var_t cpu_isolated_map;
> +cpumask_var_t non_isolated_cpus;
>
> /*
> * __task_rq_lock - lock the rq @p resides on.
> @@ -5685,8 +5686,6 @@ static inline void sched_init_smt(void)
>
> void __init sched_init_smp(void)
> {
> - cpumask_var_t non_isolated_cpus;
> -
> alloc_cpumask_var(&non_isolated_cpus, GFP_KERNEL);
>
> sched_init_numa();
> @@ -5697,17 +5696,17 @@ void __init sched_init_smp(void)
> * happen.
> */
> mutex_lock(&sched_domains_mutex);
> - sched_init_domains(cpu_active_mask);
> cpumask_andnot(non_isolated_cpus, cpu_possible_mask,
> cpu_isolated_map);
> if (cpumask_empty(non_isolated_cpus))
> cpumask_set_cpu(smp_processor_id(), non_isolated_cpus);
> +
> + sched_init_domains(cpu_active_mask);
> mutex_unlock(&sched_domains_mutex);
>
> /* Move init over to a non-isolated CPU */
> if (set_cpus_allowed_ptr(current, non_isolated_cpus) < 0)
> BUG();
> sched_init_granularity();
> - free_cpumask_var(non_isolated_cpus);
>
> init_sched_rt_class();
> init_sched_dl_class();
> --- a/kernel/sched/debug.c
> +++ b/kernel/sched/debug.c
> @@ -327,6 +327,8 @@ static struct ctl_table *sd_alloc_ctl_cp
> return table;
> }
>
> +extern cpumask_var_t non_isolated_cpus;
> +
> static struct ctl_table_header *sd_sysctl_header; void
> register_sched_domain_sysctl(void)
> {
> @@ -340,7 +342,7 @@ void register_sched_domain_sysctl(void)
> if (entry == NULL)
> return;
>
> - for_each_possible_cpu(i) {
> + for_each_cpu(i, non_isolated_cpus) {
> snprintf(buf, 32, "cpu%d", i);
> entry->procname = kstrdup(buf, GFP_KERNEL);
> entry->mode = 0555;
next prev parent reply other threads:[~2017-08-10 7:40 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-08-06 5:53 hotplug support for arch/arc/plat-eznps platform Ofer Levi(SW)
2017-08-07 8:33 ` Peter Zijlstra
2017-08-07 13:41 ` Ofer Levi(SW)
2017-08-07 15:10 ` Peter Zijlstra
2017-08-08 6:49 ` Ofer Levi(SW)
2017-08-08 10:16 ` Peter Zijlstra
2017-08-09 15:19 ` Ofer Levi(SW)
2017-08-09 15:34 ` Peter Zijlstra
2017-08-10 7:40 ` Ofer Levi(SW) [this message]
2017-08-10 9:19 ` Peter Zijlstra
2017-08-10 11:51 ` Ofer Levi(SW)
2017-08-10 15:45 ` Peter Zijlstra
2017-08-14 7:54 ` Ofer Levi(SW)
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