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

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Message-ID: <6eb2a745-7b92-73ce-46f5-cc6a5ef08abc@grimberg.me>
Date:   Fri, 6 Sep 2019 11:30:57 -0700
From:   Sagi Grimberg <sagi@...mberg.me>
To:     Daniel Lezcano <daniel.lezcano@...aro.org>,
        Ming Lei <ming.lei@...hat.com>
Cc:     Jens Axboe <axboe@...com>, Hannes Reinecke <hare@...e.com>,
        Bart Van Assche <bvanassche@....org>,
        linux-scsi@...r.kernel.org, Peter Zijlstra <peterz@...radead.org>,
        Long Li <longli@...rosoft.com>,
        John Garry <john.garry@...wei.com>,
        LKML <linux-kernel@...r.kernel.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


> 
> Ok, so the real problem is per-cpu bounded tasks.
> 
> I share Thomas opinion about a NAPI like approach.

We already have that, its irq_poll, but it seems that for this
use-case, we get lower performance for some reason. I'm not
entirely sure why that is, maybe its because we need to mask interrupts
because we don't have an "arm" register in nvme like network devices
have?