netdev - Re: [REGRESSION, bisect]cxgb4 port failure with TSO traffic after commit 10d3be569243def8("tcp-tso: do not split TSO packets at retransmit time")

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Message-ID: <20160627085957.GB13319@v4.asicdesigners.com>
Date:	Mon, 27 Jun 2016 14:29:58 +0530
From:	Arjun V <arjun@...lsio.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	Eric Dumazet <edumazet@...gle.com>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	Hariprasad S <hariprasad@...lsio.com>,
	Casey Leedom <leedom@...lsio.com>,
	Kumar A S <kumaras@...lsio.com>,
	Santosh Rastapur <santosh@...lsio.com>,
	Nirranjan Kirubaharan <nirranjan@...lsio.com>,
	"davem@...emloft.net" <davem@...emloft.net>,
	"ycheng@...gle.com" <ycheng@...gle.com>
Subject: Re: [REGRESSION, bisect]cxgb4 port failure with TSO traffic after
 commit 10d3be569243def8("tcp-tso: do not split TSO packets at retransmit
 time")

On Monday, June 06/27/16, 2016 at 13:36:22 +0530, Eric Dumazet wrote:
> On Mon, 2016-06-27 at 12:47 +0530, Arjun V wrote:
> 
> > Eric,
> > 
> > Thanks for the quick patch. It didn't help much. We still see packets larger than 65536 with the patch.
> > 
> > Below is the dump_stack() trace I am seeing for packets larger than 65536 in our xmit routine:
> 
> What values do you get for skb->len ?
>
These are the skb->len values I am hitting in t4_eth_xmit() for around half hour run of netperf bidi(800 connections total)
packet with skb->len 69570 detected
packet with skb->len 66674 detected
packet with skb->len 68122 detected
packet with skb->len 68122 detected
packet with skb->len 72466 detected
packet with skb->len 76810 detected
packet with skb->len 69570 detected
packet with skb->len 66674 detected
packet with skb->len 66674 detected
packet with skb->len 68122 detected
packet with skb->len 71018 detected
packet with skb->len 66674 detected
packet with skb->len 66674 detected
packet with skb->len 66674 detected
packet with skb->len 69570 detected
packet with skb->len 68122 detected
packet with skb->len 73914 detected
packet with skb->len 66674 detected
packet with skb->len 69570 detected
packet with skb->len 69570 detected
packet with skb->len 69570 detected
packet with skb->len 68122 detected
packet with skb->len 72466 detected
packet with skb->len 68122 detected
packet with skb->len 69570 detected
packet with skb->len 69570 detected
packet with skb->len 72466 detected
packet with skb->len 72466 detected

> Again, at retransmit time we never grow packets, we only can split
> existing packets. So there is something very wrong.
> 
> The original xmit should already have hit this issue.
> 
> 
>