From patchwork Fri Sep 5 01:49:19 2014 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Rusty Russell X-Patchwork-Id: 386089 X-Patchwork-Delegate: davem@davemloft.net Return-Path: X-Original-To: patchwork-incoming@ozlabs.org Delivered-To: patchwork-incoming@ozlabs.org Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by ozlabs.org (Postfix) with ESMTP id 8CFC21400EA for ; Fri, 5 Sep 2014 12:35:09 +1000 (EST) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755919AbaIECex (ORCPT ); Thu, 4 Sep 2014 22:34:53 -0400 Received: from ozlabs.org ([103.22.144.67]:40807 "EHLO ozlabs.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755862AbaIECev (ORCPT ); Thu, 4 Sep 2014 22:34:51 -0400 Received: by ozlabs.org (Postfix, from userid 1011) id 242DF14009C; Fri, 5 Sep 2014 12:34:50 +1000 (EST) From: Rusty Russell To: Jesper Dangaard Brouer Cc: netdev , Mathias Krause , brouer@redhat.com, Robert Olsson Subject: Re: [PATCH] pktgen: nowait parameter. In-Reply-To: <20140903110956.0872841f@redhat.com> References: <87oauxibda.fsf@rustcorp.com.au> <20140903110956.0872841f@redhat.com> User-Agent: Notmuch/0.17 (http://notmuchmail.org) Emacs/24.3.1 (x86_64-pc-linux-gnu) Date: Fri, 05 Sep 2014 11:19:19 +0930 Message-ID: <87sik6kfa8.fsf@rustcorp.com.au> MIME-Version: 1.0 Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org Jesper Dangaard Brouer writes: > On Wed, 03 Sep 2014 13:50:01 +0930 > Rusty Russell wrote: > >> 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. > > This pktgen_wait_for_skb() only happens it the exit case, when count > packets have been send. I guess its okay to proceed to > pktgen_stop_device() which will call kfree_skb(pkt_dev->skb) with > refcnt=2, decrementing to refcnt=1, and then we depend on driver to > eventually call kfree_skb(). Yes, exactly. >> 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). > > Yes, the doc is not in such a good shape. > > I'm not 100% happy with the name "nowait" parameter, as users could > easily misunderstand the purpose of this parameter. But I've not come > up with a better name, e.g. "exit_nowait" is also not the best. Agreed. It could also be a flag, though that doesn't help with the name. > 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 >> + */ >> + > > DaveM prefers multi line comments like: > > /* Don't wait for packet to be freed > * by driver > */ He does, but the rest of the kernel and the comment immediately above doesn't: int clone_skb; /* * Use multiple SKBs during packet gen. * If this number is greater than 1, then * that many copies of the same packet will be * sent before a new packet is allocated. * If you want to send 1024 identical packets * before creating a new packet, * set clone_skb to 1024. */ >> 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"); >> + > > Shouldn't you put this print statement above the "Flags:" section? Sure. >> /* 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, Subject: pktgen: nowait parameter. 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 --- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html diff --git a/Documentation/networking/pktgen.txt b/Documentation/networking/pktgen.txt index 0dffc6e37902..dbd993d1e7f8 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 +306,8 @@ 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..1589f5ac0509 100644 --- a/net/core/pktgen.c +++ b/net/core/pktgen.c @@ -290,6 +290,8 @@ 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 */ @@ -615,6 +617,9 @@ static int pktgen_if_show(struct seq_file *seq, void *v) if (pkt_dev->node >= 0) seq_printf(seq, " node: %d\n", pkt_dev->node); + if (pkt_dev->no_wait) + seq_puts(seq, " nowait\n"); + seq_puts(seq, " Flags: "); if (pkt_dev->flags & F_IPV6) @@ -1711,6 +1716,17 @@ 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 +3389,8 @@ 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 +3582,7 @@ 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)