linux-kernel - Re: [PATCH v2] nvme/tcp: Add support to set the tcp worker cpu affinity

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Message-ID: <ZDz3TlFUxMxaO1W4@ovpn-8-16.pek2.redhat.com>
Date:   Mon, 17 Apr 2023 15:37:50 +0800
From:   Ming Lei <ming.lei@...hat.com>
To:     Li Feng <fengli@...rtx.com>
Cc:     Keith Busch <kbusch@...nel.org>, Jens Axboe <axboe@...com>,
        Christoph Hellwig <hch@....de>,
        Sagi Grimberg <sagi@...mberg.me>,
        "open list:NVM EXPRESS DRIVER" <linux-nvme@...ts.infradead.org>,
        open list <linux-kernel@...r.kernel.org>, lifeng1519@...il.com,
        ming.lei@...hat.com
Subject: Re: [PATCH v2] nvme/tcp: Add support to set the tcp worker cpu
 affinity

On Thu, Apr 13, 2023 at 09:29:41PM +0800, Li Feng wrote:
> The default worker affinity policy is using all online cpus, e.g. from 0
> to N-1. However, some cpus are busy for other jobs, then the nvme-tcp will
> have a bad performance.

Can you explain in detail how nvme-tcp performs worse in this situation?

If some of CPUs are knows as busy, you can submit the nvme-tcp io jobs
on other non-busy CPUs via taskset, or scheduler is supposed to choose
proper CPUs for you. And usually nvme-tcp device should be saturated
with limited io depth or jobs/cpus.


Thanks, 
Ming