linux-kernel - Re: [PATCH v4 5/5] vsock/virtio: change the maximum packet size allowed

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Message-ID: <20190718083105-mutt-send-email-mst@kernel.org>
Date:   Thu, 18 Jul 2019 08:33:40 -0400
From:   "Michael S. Tsirkin" <mst@...hat.com>
To:     Stefano Garzarella <sgarzare@...hat.com>
Cc:     netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        Stefan Hajnoczi <stefanha@...hat.com>,
        "David S. Miller" <davem@...emloft.net>,
        virtualization@...ts.linux-foundation.org,
        Jason Wang <jasowang@...hat.com>, kvm@...r.kernel.org
Subject: Re: [PATCH v4 5/5] vsock/virtio: change the maximum packet size
 allowed

On Thu, Jul 18, 2019 at 09:52:41AM +0200, Stefano Garzarella wrote:
> On Wed, Jul 17, 2019 at 5:00 PM Michael S. Tsirkin <mst@...hat.com> wrote:
> >
> > On Wed, Jul 17, 2019 at 01:30:30PM +0200, Stefano Garzarella wrote:
> > > Since now we are able to split packets, we can avoid limiting
> > > their sizes to VIRTIO_VSOCK_DEFAULT_RX_BUF_SIZE.
> > > Instead, we can use VIRTIO_VSOCK_MAX_PKT_BUF_SIZE as the max
> > > packet size.
> > >
> > > Signed-off-by: Stefano Garzarella <sgarzare@...hat.com>
> >
> >
> > OK so this is kind of like GSO where we are passing
> > 64K packets to the vsock and then split at the
> > low level.
> 
> Exactly, something like that in the Host->Guest path, instead in the
> Guest->Host we use the entire 64K packet.
> 
> Thanks,
> Stefano

btw two allocations for each packet isn't great. How about
allocating the struct linearly with the data?
And all buffers are same length for you - so you can actually
do alloc_pages.
Allocating/freeing pages in a batch should also be considered.

-- 
MST