netdev - Re: [net-next PATCH 2/5] ixgbe: increase default TX ring buffer to 1024

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Message-ID: <20140514212512.196b5136@redhat.com>
Date:	Wed, 14 May 2014 21:25:12 +0200
From:	Jesper Dangaard Brouer <brouer@...hat.com>
To:	David Laight <David.Laight@...LAB.COM>
Cc:	brouer@...hat.com,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	Alexander Duyck <alexander.h.duyck@...el.com>,
	Jeff Kirsher <jeffrey.t.kirsher@...el.com>,
	Daniel Borkmann <dborkman@...hat.com>,
	"Florian Westphal" <fw@...len.de>,
	"David S. Miller" <davem@...emloft.net>,
	"Stephen Hemminger" <shemminger@...tta.com>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Robert Olsson <robert@...julf.se>,
	Ben Greear <greearb@...delatech.com>,
	John Fastabend <john.r.fastabend@...el.com>,
	"danieltt@....se" <danieltt@....se>,
	"zhouzhouyi@...il.com" <zhouzhouyi@...il.com>
Subject: Re: [net-next PATCH 2/5] ixgbe: increase default TX ring buffer to
 1024

On Wed, 14 May 2014 14:28:24 +0000
David Laight <David.Laight@...LAB.COM> wrote:

> From: Jesper Dangaard Brouer
> > Using pktgen I'm seeing the ixgbe driver "push-back", due TX ring
> > running full.  Thus, the TX ring is artificially limiting pktgen.
> > 
> > Diagnose via "ethtool -S", look for "tx_restart_queue" or "tx_busy"
> > counters.
> 
> Have you tried reducing the tx interrupt mitigation delay.
> It might just be that the end of tx interrupt is delayed too long.

Does the ixgbe have TX interrupt mitigation delays?

I don't "see" them:

$ sudo ethtool -c eth8 
Coalesce parameters for eth8:
Adaptive RX: off  TX: off
stats-block-usecs: 0
sample-interval: 0
pkt-rate-low: 0
pkt-rate-high: 0

rx-usecs: 1
rx-frames: 0
rx-usecs-irq: 0
rx-frames-irq: 0

tx-usecs: 0
tx-frames: 0
tx-usecs-irq: 0
tx-frames-irq: 0

rx-usecs-low: 0
rx-frame-low: 0
tx-usecs-low: 0
tx-frame-low: 0

rx-usecs-high: 0
rx-frame-high: 0
tx-usecs-high: 0
tx-frame-high: 0


-- 
Best regards,
  Jesper Dangaard Brouer
  MSc.CS, Sr. Network Kernel Developer at Red Hat
  Author of http://www.iptv-analyzer.org
  LinkedIn: http://www.linkedin.com/in/brouer
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