linux-kernel - Re: NVME performance regression in Linux 5.x due to lack of block level IO queueing

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Date:   Fri, 1 Apr 2022 02:59:00 +0000
From:   Chaitanya Kulkarni <chaitanyak@...dia.com>
To:     Michael Marod <michael@...haelmarod.com>
CC:     Keith Busch <kbusch@...nel.org>,
        Christoph Hellwig <hch@...radead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-block@...r.kernel.org" <linux-block@...r.kernel.org>
Subject: Re: NVME performance regression in Linux 5.x due to lack of block
 level IO queueing


> Thanks for the info. I don't know of anything block or nvme specific that might
> explain an order of magnitude perf difference.
> 
> Could you try the same test without the filesytems? You mentioned using mdraid,
> so try '--filename=/dev/mdX'. If that also shows similiar performance
> difference, try using one of your nvme member drives directly, like
> '--filename=/dev/nvme1n1'. That should isolate which subsystem is contributing
> to the difference.
> 

With Keith's suggestions you can always take the perf numbers and
compare before and after mainly for nvme_queue_rq() and nvme_irq().

-ck