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

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Message-ID: <a2eff7fd-5670-8c15-a72a-589fe7d99f31@grimberg.me>
Date:   Thu, 27 Apr 2023 15:21:30 +0300
From:   Sagi Grimberg <sagi@...mberg.me>
To:     Hannes Reinecke <hare@...e.de>, Li Feng <fengli@...rtx.com>
Cc:     Keith Busch <kbusch@...nel.org>, Jens Axboe <axboe@...com>,
        Christoph Hellwig <hch@....de>,
        "open list:NVM EXPRESS DRIVER" <linux-nvme@...ts.infradead.org>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] nvme/tcp: Add support to set the tcp worker cpu affinity


>>> Not saying that this should be a solution though.
>>>
>>> How many queues does your controller support that you happen to use
>>> queue 0 ?
>> Our controller only support one io queue currently.
> 
> Ouch.
> Remember, NVMe gets most of the performance improvements by using 
> several queues, and be able to bind the queues to cpu sets.
> Exposing just one queue will be invalidating any assumptions we do,
> and trying to improve interrupt steering won't work anyway.
> 
> I sincerely doubt we should try to 'optimize' for this rather peculiar 
> setup.

I tend to agree. This is not a common setup that I'm particularly
interested in exporting something dedicated in the driver for fiddling
with it...