linux-kernel - Re: [PATCH 1/4] softirq: implement IRQ flood detection mechanism

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Date:   Fri, 6 Sep 2019 06:36:23 +0200
From:   Daniel Lezcano <daniel.lezcano@...aro.org>
To:     Long Li <longli@...rosoft.com>, Ming Lei <ming.lei@...hat.com>
Cc:     Bart Van Assche <bvanassche@....org>, Jens Axboe <axboe@...com>,
        Hannes Reinecke <hare@...e.com>,
        Sagi Grimberg <sagi@...mberg.me>,
        "linux-scsi@...r.kernel.org" <linux-scsi@...r.kernel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        John Garry <john.garry@...wei.com>,
        LKML <linux-kernel@...r.kernel.org>,
        "linux-nvme@...ts.infradead.org" <linux-nvme@...ts.infradead.org>,
        Keith Busch <keith.busch@...el.com>,
        Ingo Molnar <mingo@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Christoph Hellwig <hch@....de>
Subject: Re: [PATCH 1/4] softirq: implement IRQ flood detection mechanism


On 06/09/2019 03:22, Long Li wrote:
[ ... ]
> 

> Tracing shows that the CPU was in either hardirq or softirq all the
> time before warnings. During tests, the system was unresponsive at
> times.
> 
> Ming's patch fixed this problem. The system was responsive throughout
> tests.
> 
> As for performance hit, both resulted in a small drop in peak IOPS.
> With IRQ_TIME_ACCOUNTING I see a 3% drop. With Ming's patch it is 1%
> drop.

Do you mean IRQ_TIME_ACCOUNTING + irq threaded ?


> For the tests, I used the following fio command on 10 NVMe disks: fio
> --bs=4k --ioengine=libaio --iodepth=128
> --filename=/dev/nvme0n1:/dev/nvme1n1:/dev/nvme2n1:/dev/nvme3n1:/dev/nvme4n1:/dev/nvme5n1:/dev/nvme6n1:/dev/nvme7n1:/dev/nvme8n1:/dev/nvme9n1
> --direct=1 --runtime=12000 --numjobs=80 --rw=randread --name=test
> --group_reporting --gtod_reduce=1

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