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From: Nitesh Narayan Lal <nitesh@redhat.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: linux-kernel@vger.kernel.org, netdev@vger.kernel.org,
	linux-pci@vger.kernel.org, intel-wired-lan@lists.osuosl.org,
	frederic@kernel.org, mtosatti@redhat.com, sassmann@redhat.com,
	jesse.brandeburg@intel.com, lihong.yang@intel.com,
	helgaas@kernel.org, jeffrey.t.kirsher@intel.com,
	jacob.e.keller@intel.com, jlelli@redhat.com, hch@infradead.org,
	bhelgaas@google.com, mike.marciniszyn@intel.com,
	dennis.dalessandro@intel.com, thomas.lendacky@amd.com,
	jiri@nvidia.com, mingo@redhat.com, juri.lelli@redhat.com,
	vincent.guittot@linaro.org, lgoncalv@redhat.com,
	Thomas Gleixner <tglx@linutronix.de>
Subject: Re: [PATCH v4 2/4] sched/isolation: Extend nohz_full to isolate managed IRQs
Date: Fri, 23 Oct 2020 09:45:53 -0400
Message-ID: <ef8fbae8-06e1-b947-30b1-281afd330f01@redhat.com> (raw)
In-Reply-To: <20201023132505.GZ2628@hirez.programming.kicks-ass.net>

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On 10/23/20 9:25 AM, Peter Zijlstra wrote:
> On Mon, Sep 28, 2020 at 02:35:27PM -0400, Nitesh Narayan Lal wrote:
>> Extend nohz_full feature set to include isolation from managed IRQS. This
> So you say it's for managed-irqs, the feature is actually called
> MANAGED_IRQ, but, AFAICT, it does *NOT* in fact affect managed IRQs.

Ah my bad! I should replace the managed IRQS with MANAGED_IRQ.
I can send another version with this fixed.

>
> Also, as per Thomas' earlier points, managed-irqs are in fact perfectly
> fine and don't need help at at...

Since the introduction of
"genirq, sched/isolation: Isolate from handling managed interrupts"

Within irq_do_set_affinity(), it is ensured that for managed intrrupts as
well, the isolated CPUs are removed from the affinity mask.

Hence, IMHO before this change managed interrupts were affecting the
isolated CPUs.

My intent of having this change is to basically allow isolation for
nohz_full CPUs even when we don't have something like isolcpus.
Does that make sense?


>
>> is required specifically for setups that only uses nohz_full and still
>> requires isolation for maintaining lower latency for the listed CPUs.
>>
>> Suggested-by: Frederic Weisbecker <frederic@kernel.org>
>> Signed-off-by: Nitesh Narayan Lal <nitesh@redhat.com>
>> ---
>>  kernel/sched/isolation.c | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/kernel/sched/isolation.c b/kernel/sched/isolation.c
>> index 5a6ea03f9882..9df9598a9e39 100644
>> --- a/kernel/sched/isolation.c
>> +++ b/kernel/sched/isolation.c
>> @@ -141,7 +141,7 @@ static int __init housekeeping_nohz_full_setup(char *str)
>>  	unsigned int flags;
>>  
>>  	flags = HK_FLAG_TICK | HK_FLAG_WQ | HK_FLAG_TIMER | HK_FLAG_RCU |
>> -		HK_FLAG_MISC | HK_FLAG_KTHREAD;
>> +		HK_FLAG_MISC | HK_FLAG_KTHREAD | HK_FLAG_MANAGED_IRQ;
>>  
>>  	return housekeeping_setup(str, flags);
>>  }
>> -- 
>> 2.18.2
>>
-- 
Nitesh


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  parent reply index

Thread overview: 55+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-09-28 18:35 [PATCH v4 0/4] isolation: limit msix vectors to housekeeping CPUs Nitesh Narayan Lal
2020-09-28 18:35 ` [PATCH v4 1/4] sched/isolation: API to get number of " Nitesh Narayan Lal
2020-09-28 18:35 ` [PATCH v4 2/4] sched/isolation: Extend nohz_full to isolate managed IRQs Nitesh Narayan Lal
2020-10-23 13:25   ` Peter Zijlstra
2020-10-23 13:29     ` Frederic Weisbecker
2020-10-23 13:57       ` Nitesh Narayan Lal
2020-10-23 13:45     ` Nitesh Narayan Lal [this message]
2020-09-28 18:35 ` [PATCH v4 3/4] i40e: Limit msix vectors to housekeeping CPUs Nitesh Narayan Lal
2020-09-28 18:35 ` [PATCH v4 4/4] PCI: Limit pci_alloc_irq_vectors() " Nitesh Narayan Lal
2020-09-28 21:59   ` Bjorn Helgaas
2020-09-29 17:46     ` Christoph Hellwig
2020-10-16 12:20   ` Peter Zijlstra
2020-10-18 18:14     ` Nitesh Narayan Lal
2020-10-19 11:11       ` Peter Zijlstra
2020-10-19 14:00         ` Marcelo Tosatti
2020-10-19 14:25           ` Nitesh Narayan Lal
2020-10-20  7:30           ` Peter Zijlstra
2020-10-20 13:00             ` Nitesh Narayan Lal
2020-10-20 13:41               ` Peter Zijlstra
2020-10-20 14:39                 ` Nitesh Narayan Lal
2020-10-22 17:47                   ` Nitesh Narayan Lal
2020-10-23  8:58                     ` Peter Zijlstra
2020-10-23 13:10                       ` Nitesh Narayan Lal
2020-10-23 21:00                         ` Thomas Gleixner
2020-10-26 13:35                           ` Nitesh Narayan Lal
2020-10-26 13:57                             ` Thomas Gleixner
2020-10-26 17:30                           ` Marcelo Tosatti
2020-10-26 19:00                             ` Thomas Gleixner
2020-10-26 19:11                               ` Marcelo Tosatti
2020-10-26 19:21                               ` Jacob Keller
2020-10-26 20:11                                 ` Thomas Gleixner
2020-10-26 21:11                                   ` Jacob Keller
2020-10-26 21:50                                     ` Thomas Gleixner
2020-10-26 22:13                                       ` Jakub Kicinski
2020-10-26 22:46                                         ` Thomas Gleixner
2020-10-26 22:52                                         ` Jacob Keller
2020-10-26 22:22                                       ` Nitesh Narayan Lal
2020-10-26 22:49                                         ` Thomas Gleixner
2020-10-26 23:08                                           ` Jacob Keller
2020-10-27 14:28                                             ` Thomas Gleixner
2020-10-27 11:47                                         ` Marcelo Tosatti
2020-10-27 14:43                                           ` Thomas Gleixner
2020-10-19 14:21         ` Frederic Weisbecker
2020-10-20 14:16   ` Thomas Gleixner
2020-10-20 16:18     ` Nitesh Narayan Lal
2020-10-20 18:07       ` Thomas Gleixner
2020-10-21 20:25         ` Thomas Gleixner
2020-10-21 21:04           ` Nitesh Narayan Lal
2020-10-22  0:02           ` Jakub Kicinski
2020-10-22  0:27             ` Jacob Keller
2020-10-22  8:28             ` Thomas Gleixner
2020-10-22 12:28           ` Marcelo Tosatti
2020-10-22 22:39             ` Thomas Gleixner
2020-10-01 15:49 ` [PATCH v4 0/4] isolation: limit msix vectors " Frederic Weisbecker
2020-10-08 21:40   ` Nitesh Narayan Lal

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