From: "Michael S. Tsirkin" <mst@redhat•com>
To: Eric Dumazet <eric.dumazet@gmail•com>
Cc: netdev@vger•kernel.org, linux-kernel@vger•kernel.org,
"David S. Miller" <davem@davemloft•net>,
"Jamal Hadi Salim" <hadi@cyberus•ca>,
"Stephen Hemminger" <shemminger@vyatta•com>,
"Jason Wang" <jasowang@redhat•com>,
"Neil Horman" <nhorman@tuxdriver•com>,
"Jiri Pirko" <jpirko@redhat•com>,
"Jeff Kirsher" <jeffrey.t.kirsher@intel•com>,
"Michał Mirosław" <mirq-linux@rere•qmqm.pl>,
"Ben Hutchings" <bhutchings@solarflare•com>,
"Herbert Xu" <herbert@gondor•hengli.com.au>
Subject: Re: [PATCH] net: orphan queued skbs if device tx can stall
Date: Thu, 12 Apr 2012 00:52:12 +0300 [thread overview]
Message-ID: <20120411215212.GA27550@redhat.com> (raw)
In-Reply-To: <1334065929.5300.40.camel@edumazet-glaptop>
On Tue, Apr 10, 2012 at 03:52:09PM +0200, Eric Dumazet wrote:
> On Tue, 2012-04-10 at 15:41 +0300, Michael S. Tsirkin wrote:
>
> > I think it's a bad interface too but it's in a userspace ABI
> > now so I suspect we are stuck with it for now. We can try deprecating
> > but we can't just drop it.
> >
>
> By the way, skb orphaning should already be done in skb_orphan_try(),
> not sure why its done again in tun_net_xmit(). Note we perform orphaning
> right before giving skb to device on premise it'll be sent (and freed)
> in a reasonable amount of time.
>
>
> With following patch, no more qdisc on top of tun device, yet user can
> change the limit (I would be curious to know if anybody changes tun
> txqueuelen and why)
Following would makes the default visible with SIOCGIFTXQLEN
same as it was + avoid branch on data path.
Didn't have time to test yet - it should achieve
same purpose, shouldn't it?
Or do I misunderstand how it's designed to work?
diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index bb8c72c..418abd1 100644
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -521,7 +521,6 @@ static void tun_net_init(struct net_device *dev)
/* Zero header length */
dev->type = ARPHRD_NONE;
dev->flags = IFF_POINTOPOINT | IFF_NOARP | IFF_MULTICAST;
- dev->tx_queue_len = TUN_READQ_SIZE; /* We prefer our own queue length */
break;
case TUN_TAP_DEV:
@@ -531,10 +530,9 @@ static void tun_net_init(struct net_device *dev)
dev->priv_flags &= ~IFF_TX_SKB_SHARING;
eth_hw_addr_random(dev);
-
- dev->tx_queue_len = TUN_READQ_SIZE; /* We prefer our own queue length */
break;
}
+ dev->tx_queue_len = 0; /* Disable qdisc queueing */
}
/* Character device part */
@@ -1143,6 +1141,12 @@ static int tun_set_iff(struct net *net, struct file *file, struct ifreq *ifr)
if (err < 0)
goto err_free_sk;
+ /*
+ * We (ab)use queue length to limit our amount of buffering.
+ * Set our own default queue length.
+ */
+ dev->tx_queue_len = TUN_READQ_SIZE;
+
if (device_create_file(&tun->dev->dev, &dev_attr_tun_flags) ||
device_create_file(&tun->dev->dev, &dev_attr_owner) ||
device_create_file(&tun->dev->dev, &dev_attr_group))
next prev parent reply other threads:[~2012-04-11 21:52 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-04-08 17:13 [PATCH] net: orphan queued skbs if device tx can stall Michael S. Tsirkin
2012-04-08 23:49 ` Herbert Xu
2012-04-09 7:28 ` Michael S. Tsirkin
2012-04-09 7:33 ` Herbert Xu
2012-04-09 7:39 ` Michael S. Tsirkin
2012-04-09 8:29 ` Herbert Xu
2012-04-09 8:34 ` Michael S. Tsirkin
2012-04-09 8:39 ` Herbert Xu
2012-04-09 8:42 ` Michael S. Tsirkin
2012-04-09 9:13 ` Eric Dumazet
2012-04-10 7:55 ` Eric Dumazet
2012-04-10 8:41 ` Michael S. Tsirkin
2012-04-10 8:55 ` Eric Dumazet
2012-04-10 9:31 ` Michael S. Tsirkin
2012-04-10 10:04 ` Eric Dumazet
2012-04-10 11:25 ` Michael S. Tsirkin
2012-04-10 11:45 ` Eric Dumazet
2012-04-10 12:41 ` Michael S. Tsirkin
2012-04-10 13:52 ` Eric Dumazet
2012-04-10 14:10 ` Michael S. Tsirkin
2012-04-11 21:52 ` Michael S. Tsirkin [this message]
2012-05-08 19:35 ` Michael S. Tsirkin
2012-05-08 19:50 ` Michael S. Tsirkin
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20120411215212.GA27550@redhat.com \
--to=mst@redhat$(echo .)com \
--cc=bhutchings@solarflare$(echo .)com \
--cc=davem@davemloft$(echo .)net \
--cc=eric.dumazet@gmail$(echo .)com \
--cc=hadi@cyberus$(echo .)ca \
--cc=herbert@gondor$(echo .)hengli.com.au \
--cc=jasowang@redhat$(echo .)com \
--cc=jeffrey.t.kirsher@intel$(echo .)com \
--cc=jpirko@redhat$(echo .)com \
--cc=linux-kernel@vger$(echo .)kernel.org \
--cc=mirq-linux@rere$(echo .)qmqm.pl \
--cc=netdev@vger$(echo .)kernel.org \
--cc=nhorman@tuxdriver$(echo .)com \
--cc=shemminger@vyatta$(echo .)com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox