netdev - Re: [PATCH v2 net-next] virtio: Fix affinity for #VCPUs != #queue pairs

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Message-ID: <CAN+hb0UqC+FFf0n+rfjAC660SBA7ZFbO4F+LKipUMRBWVbHJjg@mail.gmail.com>
Date:   Wed, 15 Feb 2017 14:13:55 -0800
From:   Benjamin Serebrin <serebrin@...gle.com>
To:     "Michael S. Tsirkin" <mst@...hat.com>
Cc:     Willem de Bruijn <willemdebruijn.kernel@...il.com>,
        Christian Borntraeger <borntraeger@...ibm.com>,
        Network Development <netdev@...r.kernel.org>,
        Jason Wang <jasowang@...hat.com>,
        David Miller <davem@...emloft.net>,
        Willem de Bruijn <willemb@...gle.com>,
        Venkatesh Srinivas <venkateshs@...gle.com>,
        "Jon Olson (Google Drive)" <jonolson@...gle.com>,
        Rick Jones <rick.jones2@....com>,
        James Mattson <jmattson@...gle.com>,
        linux-s390 <linux-s390@...r.kernel.org>,
        "linux-arch@...r.kernel.org" <linux-arch@...r.kernel.org>
Subject: Re: [PATCH v2 net-next] virtio: Fix affinity for #VCPUs != #queue pairs

On Wed, Feb 15, 2017 at 1:49 PM, Michael S. Tsirkin <mst@...hat.com> wrote:

> The logic is simple really. With #VCPUs == #queues we can reasonably
> assume this box is mostly doing networking so we can set affinity
> the way we like. With VCPUs > queues clearly VM is doing more stuff
> so we need a userspace policy to take that into account,
> we don't know ourselves what is the right thing to do.
>
> Arguably for #VCPUs == #queues we are not always doing the right thing
> either but I see this as an argument to move more smarts
> into core kernel not for adding more dumb heuristics in the driver.

Thanks for all the feedback, Michael.  We'll drop this patch and move
to user mode.

Thanks,
Ben