From mboxrd@z Thu Jan 1 00:00:00 1970 From: Rusty Russell Subject: Re: [PATCH 2/2] virtio_net: remove send completion interrupts and avoid TX queue overrun through packet drop Date: Mon, 04 Apr 2011 15:43:41 +0930 Message-ID: <87mxk6bl2i.fsf@rustcorp.com.au> References: <20110318133311.GA20623@gondor.apana.org.au> <1300498915.3441.21.camel@localhost.localdomain> <1300730587.3441.24.camel@localhost.localdomain> <20110322113649.GA17071@redhat.com> <1300847204.3441.26.camel@localhost.localdomain> <87r59xbbr6.fsf@rustcorp.com.au> <20110324142822.GD12958@redhat.com> <87mxkjls61.fsf@rustcorp.com.au> <20110327075254.GA3776@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Shirley Ma , Herbert Xu , davem@davemloft.net, kvm@vger.kernel.org, netdev@vger.kernel.org To: "Michael S. Tsirkin" Return-path: Received: from ozlabs.org ([203.10.76.45]:35233 "EHLO ozlabs.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753699Ab1DDHDt (ORCPT ); Mon, 4 Apr 2011 03:03:49 -0400 In-Reply-To: <20110327075254.GA3776@redhat.com> Sender: kvm-owner@vger.kernel.org List-ID: On Sun, 27 Mar 2011 09:52:54 +0200, "Michael S. Tsirkin" wrote: > > Though IIRC, qemu's virtio barfs if the first descriptor isn't just the > > hdr (barf...). > > Maybe we can try fixing this before adding more flags, > then e.g. publish used flag can be resued to also > tell us layout is flexible. Or just add a feature flag for that. We should probably do this at some stage, yes. > > > 2. I didn't have time to work on virtio2 ideas presented > > > at the kvm forum yet, any takers? > > > > I didn't even attend. > > Hmm, right. But what was presented there was discussed on list as well: > a single R/W descriptor ring with valid bit instead of 2 rings > + a descriptor array. I'll be happy when we reach the point that the extra cacheline is hurting us :) Then we should do direct descriptors w/ a cookie as the value to hand back when finished. That seems to be close to optimal. > I agree absolutely that not all lessons has been learned, > playing with different ring layouts would make at least > an interesting paper IMO. Yes, I'd like to see the results... Thanks, Rusty.