From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ben Hutchings Subject: Re: [RFC] [ver3 PATCH 3/6] virtio_net: virtio_net driver changes Date: Fri, 18 Nov 2011 15:40:39 +0000 Message-ID: <1321630839.2885.117.camel@deadeye> References: <20111111130223.9878.59517.sendpatchset@krkumar2.in.ibm.com> <20111111130420.9878.19729.sendpatchset@krkumar2.in.ibm.com> <1321578488.2749.66.camel@bwh-desktop> <1321597481.8010.19.camel@lappy> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Cc: Krishna Kumar , , , , , , To: Sasha Levin Return-path: Received: from exchange.solarflare.com ([216.237.3.220]:30950 "EHLO exchange.solarflare.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758048Ab1KRPks (ORCPT ); Fri, 18 Nov 2011 10:40:48 -0500 In-Reply-To: <1321597481.8010.19.camel@lappy> Sender: netdev-owner@vger.kernel.org List-ID: On Fri, 2011-11-18 at 08:24 +0200, Sasha Levin wrote: > On Fri, 2011-11-18 at 01:08 +0000, Ben Hutchings wrote: > > On Fri, 2011-11-11 at 18:34 +0530, Krishna Kumar wrote: > > > Changes for multiqueue virtio_net driver. > > [...] > > > @@ -677,25 +730,35 @@ static struct rtnl_link_stats64 *virtnet > > > { > > > struct virtnet_info *vi = netdev_priv(dev); > > > int cpu; > > > - unsigned int start; > > > > > > for_each_possible_cpu(cpu) { > > > - struct virtnet_stats __percpu *stats > > > - = per_cpu_ptr(vi->stats, cpu); > > > - u64 tpackets, tbytes, rpackets, rbytes; > > > - > > > - do { > > > - start = u64_stats_fetch_begin(&stats->syncp); > > > - tpackets = stats->tx_packets; > > > - tbytes = stats->tx_bytes; > > > - rpackets = stats->rx_packets; > > > - rbytes = stats->rx_bytes; > > > - } while (u64_stats_fetch_retry(&stats->syncp, start)); > > > - > > > - tot->rx_packets += rpackets; > > > - tot->tx_packets += tpackets; > > > - tot->rx_bytes += rbytes; > > > - tot->tx_bytes += tbytes; > > > + int qpair; > > > + > > > + for (qpair = 0; qpair < vi->num_queue_pairs; qpair++) { > > > + struct virtnet_send_stats __percpu *tx_stat; > > > + struct virtnet_recv_stats __percpu *rx_stat; > > > > While you're at it, you can drop the per-CPU stats and make them only > > per-queue. There is unlikely to be any benefit in maintaining them > > per-CPU while receive and transmit processing is serialised per-queue. > > It allows you to update stats without a lock. But you'll already be holding a lock related to the queue. > Whats the benefit of having them per queue? It should save some memory (and a little time when summing stats, though that's unlikely to matter much). The important thing is that splitting up stats per-CPU *and* per-queue is a waste. Ben. -- Ben Hutchings, Staff Engineer, Solarflare Not speaking for my employer; that's the marketing department's job. They asked us to note that Solarflare product names are trademarked.