From mboxrd@z Thu Jan 1 00:00:00 1970 From: Rusty Russell Subject: [PATCH] pktgen: nowait parameter. Date: Wed, 03 Sep 2014 13:50:01 +0930 Message-ID: <87oauxibda.fsf@rustcorp.com.au> Mime-Version: 1.0 Content-Type: text/plain Cc: Jesper Dangaard Brouer , Mathias Krause To: "netdev" Return-path: Received: from ozlabs.org ([103.22.144.67]:44506 "EHLO ozlabs.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751541AbaICEaM (ORCPT ); Wed, 3 Sep 2014 00:30:12 -0400 Sender: netdev-owner@vger.kernel.org List-ID: While trying to measure speed of virtio_net, I was getting hangs. This is because we skb_orphan() but delay the tx interrupt indefinitely (by number of slots). With nowait, pktgen won't wait for the skb to be released. This introduces an error, but it's ok if count >> ringsize. I updated the documentation, but it needs far more work (it refers to pgset and an examples directory, none of which exist in the kernel tree). Signed-off-by: Rusty Russell diff --git a/Documentation/networking/pktgen.txt b/Documentation/networking/pktgen.txt index 0dffc6e37902..48d86da74a39 100644 --- a/Documentation/networking/pktgen.txt +++ b/Documentation/networking/pktgen.txt @@ -41,10 +41,13 @@ NIC HW layer (which is bad for bufferbloat). One should be careful to conclude, that packets/descriptors in the HW TX ring cause delay. Drivers usually delay cleaning up the ring-buffers (for various performance reasons), thus packets stalling -the TX ring, might just be waiting for cleanup. +the TX ring, might just be waiting for cleanup. Writing the "nowait" +parameter into /proc/net/pktgen/ethX will avoid waiting for cleanup of +the final packets, introducing a slight error (tiny if the count of +packets being sent is much greater than the ring size of the device). -This cleanup issues is specifically the case, for the driver ixgbe -(Intel 82599 chip). This driver (ixgbe) combine TX+RX ring cleanups, +Alternately, some drivers (eg ixgbe for the Intel 82599 chip) can +have their cleanup interval changed. ixgbe combines TX+RX ring cleanups, and the cleanup interval is affected by the ethtool --coalesce setting of parameter "rx-usecs". @@ -303,6 +305,8 @@ flowlen rate ratep +nowait + References: ftp://robur.slu.se/pub/Linux/net-development/pktgen-testing/ ftp://robur.slu.se/pub/Linux/net-development/pktgen-testing/examples/ diff --git a/net/core/pktgen.c b/net/core/pktgen.c index 8b849ddfef2e..adc41f2b3bc7 100644 --- a/net/core/pktgen.c +++ b/net/core/pktgen.c @@ -290,6 +290,11 @@ struct pktgen_dev { * set clone_skb to 1024. */ + bool no_wait; /* + * Don't wait for packet to be freed + * by driver + */ + char dst_min[IP_NAME_SZ]; /* IP, ie 1.2.3.4 */ char dst_max[IP_NAME_SZ]; /* IP, ie 1.2.3.4 */ char src_min[IP_NAME_SZ]; /* IP, ie 1.2.3.4 */ @@ -679,6 +684,9 @@ static int pktgen_if_show(struct seq_file *seq, void *v) seq_puts(seq, "\n"); + if (pkt_dev->no_wait) + seq_puts(seq, " nowait\n"); + /* not really stopped, more like last-running-at */ stopped = pkt_dev->running ? ktime_get() : pkt_dev->stopped_at; idle = pkt_dev->idle_acc; @@ -1711,6 +1719,17 @@ static ssize_t pktgen_if_write(struct file *file, return count; } + if (!strcmp(name, "nowait")) { + len = num_arg(&user_buffer[i], 10, &value); + if (len < 0) + return len; + + i += len; + pkt_dev->no_wait = value; + sprintf(pg_result, "OK: nowait=%u", pkt_dev->no_wait); + return count; + } + sprintf(pkt_dev->result, "No such parameter \"%s\"", name); return -EINVAL; } @@ -3373,7 +3392,8 @@ unlock: /* If pkt_dev->count is zero, then run forever */ if ((pkt_dev->count != 0) && (pkt_dev->sofar >= pkt_dev->count)) { - pktgen_wait_for_skb(pkt_dev); + if (!pkt_dev->no_wait) + pktgen_wait_for_skb(pkt_dev); /* Done with this */ pktgen_stop_device(pkt_dev); @@ -3565,6 +3585,7 @@ static int pktgen_add_device(struct pktgen_thread *t, const char *ifname) pkt_dev->svlan_cfi = 0; pkt_dev->svlan_id = 0xffff; pkt_dev->node = -1; + pkt_dev->no_wait = false; err = pktgen_setup_dev(t->net, pkt_dev, ifname); if (err)