From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Michael S. Tsirkin" Subject: Re: [PATCH 2/4] [RFC] virtio: Introduce new API to get free space Date: Wed, 4 May 2011 22:58:18 +0300 Message-ID: <20110504195818.GA20255@redhat.com> References: <20110504140258.14817.66596.sendpatchset@krkumar2.in.ibm.com> <20110504140319.14817.23145.sendpatchset@krkumar2.in.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: davem@davemloft.net, eric.dumazet@gmail.com, kvm@vger.kernel.org, netdev@vger.kernel.org, rusty@rustcorp.com.au, mashirle@us.ibm.com To: Krishna Kumar Return-path: Received: from mx1.redhat.com ([209.132.183.28]:22067 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755357Ab1EDT65 (ORCPT ); Wed, 4 May 2011 15:58:57 -0400 Content-Disposition: inline In-Reply-To: <20110504140319.14817.23145.sendpatchset@krkumar2.in.ibm.com> Sender: kvm-owner@vger.kernel.org List-ID: On Wed, May 04, 2011 at 07:33:19PM +0530, Krishna Kumar wrote: > @@ -185,11 +193,6 @@ int virtqueue_add_buf_gfp(struct virtque > if (vq->num_free < out + in) { > pr_debug("Can't add buf len %i - avail = %i\n", > out + in, vq->num_free); > - /* FIXME: for historical reasons, we force a notify here if > - * there are outgoing parts to the buffer. Presumably the > - * host should service the ring ASAP. */ > - if (out) > - vq->notify(&vq->vq); > END_USE(vq); > return -ENOSPC; > } I thought about it some more. We should typically not get into this state with the current driver as we check capacity upfront. So why would this change help performance? Shirley, any idea? -- MST