From: Daniel Lezcano <daniel.lezcano@linaro.org>
To: Ming Lei <ming.lei@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>,
LKML <linux-kernel@vger.kernel.org>,
Long Li <longli@microsoft.com>, Ingo Molnar <mingo@redhat.com>,
Peter Zijlstra <peterz@infradead.org>,
Keith Busch <keith.busch@intel.com>, Jens Axboe <axboe@fb.com>,
Christoph Hellwig <hch@lst.de>, Sagi Grimberg <sagi@grimberg.me>,
John Garry <john.garry@huawei.com>,
Hannes Reinecke <hare@suse.com>,
linux-nvme@lists.infradead.org, linux-scsi@vger.kernel.org
Subject: Re: [PATCH 1/4] softirq: implement IRQ flood detection mechanism
Date: Tue, 3 Sep 2019 09:50:06 +0200 [thread overview]
Message-ID: <dd96def4-1121-afbe-2431-9e516a06850c@linaro.org> (raw)
In-Reply-To: <20190903072848.GA22170@ming.t460p>
On 03/09/2019 09:28, Ming Lei wrote:
> On Tue, Sep 03, 2019 at 08:40:35AM +0200, Daniel Lezcano wrote:
>> On 03/09/2019 08:31, Ming Lei wrote:
>>> Hi Daniel,
>>>
>>> On Tue, Sep 03, 2019 at 07:59:39AM +0200, Daniel Lezcano wrote:
>>>>
>>>> Hi Ming Lei,
>>>>
>>>> On 03/09/2019 05:30, Ming Lei wrote:
>>>>
>>>> [ ... ]
>>>>
>>>>
>>>>>>> 2) irq/timing doesn't cover softirq
>>>>>>
>>>>>> That's solvable, right?
>>>>>
>>>>> Yeah, we can extend irq/timing, but ugly for irq/timing, since irq/timing
>>>>> focuses on hardirq predication, and softirq isn't involved in that
>>>>> purpose.
>>>>>
>>>>>>
>>>>>>> Daniel, could you take a look and see if irq flood detection can be
>>>>>>> implemented easily by irq/timing.c?
>>>>>>
>>>>>> I assume you can take a look as well, right?
>>>>>
>>>>> Yeah, I have looked at the code for a while, but I think that irq/timing
>>>>> could become complicated unnecessarily for covering irq flood detection,
>>>>> meantime it is much less efficient for detecting IRQ flood.
>>>>
>>>> In the series, there is nothing describing rigorously the problem (I can
>>>> only guess) and why the proposed solution solves it.
>>>>
>>>> What is your definition of an 'irq flood'? A high irq load? An irq
>>>> arriving while we are processing the previous one in the bottom halves?
>>>
>>> So far, it means that handling interrupt & softirq takes all utilization
>>> of one CPU, then processes can't be run on this CPU basically, usually
>>> sort of CPU lockup warning will be triggered.
>>
>> It is a scheduler problem then ?
>
> Scheduler can do nothing if the CPU is taken completely by handling
> interrupt & softirq, so seems not a scheduler problem, IMO.
Why? If there is a irq pressure on one CPU reducing its capacity, the
scheduler will balance the tasks on another CPU, no?
--
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next prev parent reply other threads:[~2019-09-03 7:50 UTC|newest]
Thread overview: 65+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-27 8:53 [PATCH 0/4] genirq/nvme: add IRQF_RESCUE_THREAD for avoiding IRQ flood Ming Lei
2019-08-27 8:53 ` [PATCH 1/4] softirq: implement IRQ flood detection mechanism Ming Lei
2019-08-27 14:42 ` Thomas Gleixner
2019-08-27 16:19 ` Thomas Gleixner
2019-08-27 23:04 ` Ming Lei
2019-08-27 23:12 ` Thomas Gleixner
2019-08-27 22:58 ` Ming Lei
2019-08-27 23:09 ` Thomas Gleixner
2019-08-28 11:06 ` Ming Lei
2019-08-28 11:23 ` Thomas Gleixner
2019-08-28 13:50 ` Ming Lei
2019-08-28 14:07 ` Thomas Gleixner
2019-09-03 3:30 ` Ming Lei
2019-09-03 5:59 ` Daniel Lezcano
2019-09-03 6:31 ` Ming Lei
2019-09-03 6:40 ` Daniel Lezcano
2019-09-03 7:28 ` Ming Lei
2019-09-03 7:50 ` Daniel Lezcano [this message]
2019-09-03 9:30 ` Ming Lei
2019-09-04 17:07 ` Bart Van Assche
2019-09-04 17:31 ` Daniel Lezcano
2019-09-04 17:38 ` Bart Van Assche
2019-09-04 18:02 ` Peter Zijlstra
2019-09-04 19:47 ` Bart Van Assche
2019-09-05 9:11 ` Ming Lei
2019-09-05 9:06 ` Ming Lei
2019-09-05 10:37 ` Daniel Lezcano
2019-09-06 1:22 ` Long Li
2019-09-06 4:36 ` Daniel Lezcano
2019-09-06 4:44 ` Long Li
2019-09-06 1:48 ` Ming Lei
2019-09-06 5:14 ` Daniel Lezcano
2019-09-06 18:30 ` Sagi Grimberg
2019-09-06 18:52 ` Keith Busch
2019-09-07 0:01 ` Ming Lei
2019-09-10 3:10 ` Sagi Grimberg
2019-09-18 0:00 ` Long Li
2019-09-20 17:14 ` Sagi Grimberg
2019-09-20 19:12 ` Long Li
2019-09-20 20:45 ` Sagi Grimberg
2019-09-24 0:57 ` Long Li
2019-09-18 14:37 ` Ming Lei
2019-09-20 17:09 ` Sagi Grimberg
2019-09-06 14:18 ` Keith Busch
2019-09-06 17:50 ` Long Li
2019-09-06 22:19 ` Ming Lei
2019-09-06 22:25 ` Keith Busch
2019-09-06 23:13 ` Ming Lei
2019-09-10 0:24 ` Ming Lei
2019-09-03 8:09 ` Thomas Gleixner
2019-09-03 9:24 ` Ming Lei
2019-08-29 6:15 ` Long Li
2019-08-30 0:55 ` Ming Lei
2019-08-27 8:53 ` [PATCH 2/4] genirq: add IRQF_RESCUE_THREAD Ming Lei
2019-08-27 8:53 ` [PATCH 3/4] nvme: pci: pass IRQF_RESCURE_THREAD to request_threaded_irq Ming Lei
2019-08-27 9:06 ` Johannes Thumshirn
2019-08-27 9:09 ` Ming Lei
2019-08-27 9:12 ` Johannes Thumshirn
2019-08-27 14:34 ` Keith Busch
2019-08-27 14:44 ` Keith Busch
2019-08-27 15:10 ` Bart Van Assche
2019-08-28 1:45 ` Ming Lei
2019-08-27 8:53 ` [PATCH 4/4] genirq: use irq's affinity for threaded irq with IRQF_RESCUE_THREAD Ming Lei
2019-08-27 14:35 ` Keith Busch
2019-09-06 8:50 ` John Garry
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