On Thu, Nov 2, 2023 at 4:56 PM Akihiko Odaki <akihiko.od...@daynix.com> wrote:
> On 2023/11/02 19:20, Yuri Benditovich wrote: > > > > > > On Thu, Nov 2, 2023 at 11:33 AM Michael S. Tsirkin <m...@redhat.com > > <mailto:m...@redhat.com>> wrote: > > > > On Thu, Nov 02, 2023 at 11:09:27AM +0200, Yuri Benditovich wrote: > > > Probably we mix two different patches in this discussion. > > > Focusing on the patch in the e-mail header: > > > > > > IMO it is not acceptable to fail QEMU run for one feature that we > > can't make > > > active when we silently drop all other features in such a case. > > > > If the feature is off by default then it seems more reasonable > > and silent masking can be seen as a bug. > > Most virtio features are on by default this is why it's > > reasonable to mask them. > > > > > > If we are talking about RSS: setting it initially off is the development > > time decision. > > When it will be completely stable there is no reason to keep it off by > > default, so this is more a question of time and of a readiness of > libvirt. > > It is not ok to make "on" the default; that will enable RSS even when > eBPF steering support is not present and can result in performance > degradation. > Exactly as it is today - with vhost=on the host does not suggest RSS without eBPF. I do not understand what you call "performance degradation", can you describe the scenario? > > We will need OnOffAuto instead of a simple boolean value if we are going > to enable RSS when eBPF steering support is available; "auto" will be > the default and will enable RSS if and only if eBPF steering support is > available. "on" will not be default so it's better to validate if RSS is > available when the user explicitly specified "on" for the "rss" property. >
