From mboxrd@z Thu Jan 1 00:00:00 1970 From: annie li Subject: Re: [Xen-devel] [PATCHv1] xen-netfront: always keep the Rx ring full of requests Date: Mon, 06 Oct 2014 11:35:46 -0400 Message-ID: <5432B6D2.9030503@oracle.com> References: <1412256826-18874-1-git-send-email-david.vrabel@citrix.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: netdev@vger.kernel.org, xen-devel@lists.xenproject.org, Boris Ostrovsky To: David Vrabel Return-path: Received: from aserp1040.oracle.com ([141.146.126.69]:49418 "EHLO aserp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751473AbaJFPf5 (ORCPT ); Mon, 6 Oct 2014 11:35:57 -0400 In-Reply-To: <1412256826-18874-1-git-send-email-david.vrabel@citrix.com> Sender: netdev-owner@vger.kernel.org List-ID: On 2014/10/2 9:33, David Vrabel wrote: > A full Rx ring only requires 1 MiB of memory. This is not enough > memory that it is useful to dynamically scale the number of Rx > requests in the ring based on traffic rates. > > Keeping the ring full of Rx requests handles bursty traffic better > than trying to converges on an optimal number of requests to keep > filled. > > On a 4 core host, an iperf -P 64 -t 60 run from dom0 to a 4 VCPU guest > improved from 5.1 Gbit/s to 5.6 Gbit/s. Gains with more bursty > traffic are expected to be higher. Although removing sysfs is connected with the code change for full Rx ring utilization, I assume it is better to split this patch into two to make it simpler? ...snip... > > + queue->rx.req_prod_pvt = req_prod; > + > + /* Not enough requests? Try again later. */ > + if (req_prod - queue->rx.rsp_cons < NET_RX_SLOTS_MIN) { > + mod_timer(&queue->rx_refill_timer, jiffies + (HZ/10)); > + return; If the previous for loop breaks because of failure of xennet_alloc_one_rx_buffer, then notify_remote_via_irq is missed here if the code returns directly. Thanks Annie > + } > +