Re: [virtio-comment] [PATCH] virtio-net: support per-queue coalescing moderation

["Michael S. Tsirkin" <mst@redhat.com>]

On Wed, Feb 08, 2023 at 02:37:55PM +0000, Parav Pandit wrote:
> 
> > From: Michael S. Tsirkin <mst@redhat.com>
> > Sent: Wednesday, February 8, 2023 9:18 AM
> > 
> > On Wed, Feb 08, 2023 at 07:30:34PM +0800, Heng Qi wrote:
> > > > I see two options.
> > > > 1. Just have per VQ params. Software has the full knowledge of in which it is
> > operating, and state remains at software level.
> > > > This effectively achieves both the mode.
> > > >
> > > > 2. Have a mode cmd,
> > > > Mode = (a) per device or (b) per VQ (c) disable After the mode is
> > > > set, driver can set per device or per VQ.
> > >
> > > I find this more clear.
> > >
> > > Thanks.
> > >
> > 
> > Rereading this I think I misunderstood the proposal.
> > Now we are burning memory on maintaining mode, and this information is
> > duplicated.
> > 
> It is not maintained in the pci resident memory, so it doesn't hurt.

It can't reasonably be read from RAM at each packet, you need to cache it
in memory.