Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752031AbbBMC55 (ORCPT ); Thu, 12 Feb 2015 21:57:57 -0500 Received: from ozlabs.org ([103.22.144.67]:54011 "EHLO ozlabs.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750973AbbBMC54 (ORCPT ); Thu, 12 Feb 2015 21:57:56 -0500 From: Rusty Russell To: "Michael S. Tsirkin" Cc: Jason Wang , netdev@vger.kernel.org, linux-kernel@vger.kernel.org, virtualization@lists.linux-foundation.org, pagupta@redhat.com, Pawel Moll , Cornelia Huck Subject: Re: [PATCH RFC v5 net-next 4/6] virtio-net: add basic interrupt coalescing support In-Reply-To: <20150210104019.GD9505@redhat.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> User-Agent: Notmuch/0.17 (http://notmuchmail.org) Emacs/24.3.1 (x86_64-pc-linux-gnu) Date: Fri, 13 Feb 2015 13:22:09 +1030 Message-ID: <874mqqbk12.fsf@rustcorp.com.au> MIME-Version: 1.0 Content-Type: text/plain Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1705 Lines: 42 "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. >> My feeling is that this should be a v1.0-only feature though >> (eg. feature bit 33). > > Yes, e.g. we can't extend config space for legacy virtio pci. Thanks, Rusty. -- 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/