From: Eric Dumazet <eric.dumazet@gmail.com>
To: Paul Gortmaker <paul.gortmaker@windriver.com>
Cc: David Miller <davem@davemloft.net>,
netdev <netdev@vger.kernel.org>, stable <stable@vger.kernel.org>,
Willy Tarreau <w@1wt.eu>, Tom Herbert <therbert@google.com>,
Steven Rostedt <rostedt@goodmis.org>
Subject: Re: [PATCH] net: reduce net_rx_action() latency to 2 HZ
Date: Thu, 21 Mar 2013 10:43:14 -0700 [thread overview]
Message-ID: <1363887794.4431.29.camel@edumazet-glaptop> (raw)
In-Reply-To: <514B429C.5070605@windriver.com>
On Thu, 2013-03-21 at 13:25 -0400, Paul Gortmaker wrote:
> That is also reasonably portable back to 2.6.34. And it is more
> interesting too -- it will be interesting in a preempt_rt context
> too, once RT moves ahead off the current 3.6 baseline, which still
> has the old count-limit of 10 vs the new 2ms time limit.
>
> RT (3.4 and 3.6 based) currently has this patch from Steven:
> http://git.kernel.org/cgit/linux/kernel/git/paulg/3.6-rt-patches.git/tree/net-tx-action-avoid-livelock-on-rt.patch
Interesting, as Google has an internal patch removing this trylock() as
well.
I think I should upstream it eventually ;)
commit 2f0a3f573b531dc57c268fd809dc65169edae369
Author: Eric Dumazet <edumazet@google.com>
Date: Thu Dec 13 09:18:01 2012 -0800
net-dev_xmit_hold_queues: fix a busy loop in net_tx_action
Under load, net_tx_action() fails to acquire qdisc lock
and reschedules qdisc in a never ending loop.
The spin_trylock() has almost no chance to complete because
of ticket spinlock and xmit_hold_queue holding the lock for long
period of times.
next prev parent reply other threads:[~2013-03-21 17:43 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-03-05 17:15 [PATCH] net: reduce net_rx_action() latency to 2 HZ Eric Dumazet
2013-03-21 15:03 ` Paul Gortmaker
2013-03-21 15:27 ` Eric Dumazet
2013-03-21 17:25 ` Paul Gortmaker
2013-03-21 17:43 ` Eric Dumazet [this message]
2013-03-21 18:45 ` Steven Rostedt
2013-03-24 1:02 ` Willy Tarreau
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