Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752894AbbBMMlS (ORCPT ); Fri, 13 Feb 2015 07:41:18 -0500 Received: from foss-mx-na.arm.com ([217.140.108.86]:43543 "EHLO foss-mx-na.foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752701AbbBMMlQ (ORCPT ); Fri, 13 Feb 2015 07:41:16 -0500 Message-ID: <1423831266.21394.1.camel@arm.com> Subject: Re: [PATCH RFC v5 net-next 4/6] virtio-net: add basic interrupt coalescing support From: Pawel Moll To: Rusty Russell 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 Date: Fri, 13 Feb 2015 12:41:06 +0000 In-Reply-To: <874mqqbk12.fsf@rustcorp.com.au> 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> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.12.7-0ubuntu1 Mime-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2015 Lines: 46 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 ethtool. > >> > >> The problem is that there's nothing network specific about interrupt > >> coalescing. I can see other devices wanting exactly the same thing, > >> which means we'd deprecate this in the next virtio standard. > >> > >> I think the right answer is to extend like we did with > >> vring_used_event(), eg: > >> > >> 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])) > >> > >> 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 could > >> change virtqueue_enable_cb_delayed() to take a precise number if we > >> wanted. > > > > But do we expect delay to be update dynamically? > > If not, why not stick it in config space? > > 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. > > 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 control 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 to do :-) Paweł -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/