From mboxrd@z Thu Jan 1 00:00:00 1970 From: Pawel Moll Subject: Re: [PATCH RFC v5 net-next 4/6] virtio-net: add basic interrupt coalescing support Date: Fri, 13 Feb 2015 12:41:06 +0000 Message-ID: <1423831266.21394.1.camel@arm.com> References: <1423471165-34243-1-git-send-email-jasowang@redhat.com> <1423471165-34243-5-git-send-email-jasowang@redhat.com> <87386ey2iy.fsf@rustcorp.com.au> <20150210104019.GD9505@redhat.com> <874mqqbk12.fsf@rustcorp.com.au> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Cc: "Michael S. Tsirkin" , Jason Wang , "netdev@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "virtualization@lists.linux-foundation.org" , "pagupta@redhat.com" , Cornelia Huck To: Rusty Russell Return-path: In-Reply-To: <874mqqbk12.fsf@rustcorp.com.au> Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org On Fri, 2015-02-13 at 02:52 +0000, Rusty Russell wrote: > "Michael S. Tsirkin" writes: > > On Tue, Feb 10, 2015 at 12:02:37PM +1030, Rusty Russell wrote: > >> Jason Wang writes: > >> > This patch enables the interrupt coalescing setting through etht= ool. > >>=20 > >> The problem is that there's nothing network specific about interru= pt > >> coalescing. I can see other devices wanting exactly the same thin= g, > >> which means we'd deprecate this in the next virtio standard. > >>=20 > >> I think the right answer is to extend like we did with > >> vring_used_event(), eg: > >>=20 > >> 1) Add a new feature VIRTIO_F_RING_COALESCE. > >> 2) Add another a 32-bit field after vring_used_event(), eg: > >> #define vring_used_delay(vr) (*(u32 *)((vr)->avail->ring[(= vr)->num + 2])) > >>=20 > >> This loses the ability to coalesce by number of frames, but we can= still > >> do number of sg entries, as we do now with used_event, and we coul= d > >> change virtqueue_enable_cb_delayed() to take a precise number if w= e > >> wanted. > > > > But do we expect delay to be update dynamically? > > If not, why not stick it in config space? >=20 > Hmm, we could update it dynamically (and will, in the case of ethtool= ). > But it won't be common, so we could append a field to > virtio_pci_common_cfg for PCI. >=20 > I think MMIO and CCW would be easy to extend too, but CC'd to check. As far as I understand the virtio_pci_common_cfg principle (just had a look, for the first time ;-), it's now an equivalent of the MMIO contro= l registers block. I see no major problem with adding another one. Or were you thinking about introducing some standard for the "real" config space? (fine with me as well - the transport will have nothing t= o do :-) Pawe=C5=82