From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Vrabel Subject: Re: [Xen-devel] [PATCHv1] xen-netfront: always keep the Rx ring full of requests Date: Tue, 7 Oct 2014 10:43:36 +0100 Message-ID: <5433B5C8.9060309@citrix.com> References: <5432B6D2.9030503@oracle.com> <5432BC96.6060709@citrix.com> <5432E26C.3020207@oracle.com> <20141006.170748.1817067290457286845.davem@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset="ISO-8859-1" Content-Transfer-Encoding: 7bit Cc: , , To: David Miller , Return-path: Received: from smtp02.citrix.com ([66.165.176.63]:7324 "EHLO SMTP02.CITRIX.COM" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752825AbaJGJnj (ORCPT ); Tue, 7 Oct 2014 05:43:39 -0400 In-Reply-To: <20141006.170748.1817067290457286845.davem@redhat.com> Sender: netdev-owner@vger.kernel.org List-ID: On 06/10/14 22:07, David Miller wrote: > From: annie li > Date: Mon, 06 Oct 2014 14:41:48 -0400 > >> >> On 2014/10/6 12:00, David Vrabel wrote: >>>>> + 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. >>> This is deliberate -- there's no point notifying the backend if there >>> aren't enough requests for the next packet. Since we don't know what >>> the next packet might be we assume it's the largest possible. >> That makes sense. >> However, the largest packet case does not happen so >> frequently. Moreover, netback checks the slots every incoming skb >> requires in xenvif_rx_ring_slots_available, not only concerning the >> largest case. An upcoming change to netback will cause it to wait for enough slots for the largest possible packet. > I have an opinion about the sysfs stuff. > > It's user facing, so even if it doesn't influence behavior any more > you have to keep the files around, just make them nops. That's a good point. David