netdev - Re: Throughput regression with `tcp: refine TSO autosizing`

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Message-ID: <1423234933.31870.140.camel@edumazet-glaptop2.roam.corp.google.com>
Date:	Fri, 06 Feb 2015 07:02:13 -0800
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	David Laight <David.Laight@...LAB.COM>
Cc:	Michal Kazior <michal.kazior@...to.com>,
	Neal Cardwell <ncardwell@...gle.com>,
	linux-wireless <linux-wireless@...r.kernel.org>,
	Network Development <netdev@...r.kernel.org>,
	"eyalpe@....mellanox.co.il" <eyalpe@....mellanox.co.il>
Subject: Re: Throughput regression with `tcp: refine TSO autosizing`

On Fri, 2015-02-06 at 14:31 +0000, David Laight wrote:
> From: Eric Dumazet
> > On Fri, 2015-02-06 at 05:53 -0800, Eric Dumazet wrote:
> > 
> > 
> > > wifi could eventually do that, providing in skb->tx_completion_delay_us
> > > the time spent in wifi driver.
> > >
> > > This way, we would have no penalty for network devices doing normal skb
> > > orphaning (loopback interface, ethernet, ...)
> > 
> > Another way would be that wifi does an automatic orphaning after 1 or
> > 2ms.
> 
> Couldn't you do byte counting?
> So orphan enough packets to keep a few ms of tx traffic (at the current
> tx rate) orphaned.
> You might need to give the hardware both orphaned and non-orphaned (parented?)
> packets and orphan some when you get a tx complete for an orphaned packet.

We already have byte counting.

The thing is : A driver can keep an skb for itself, but calling
skb_orphan() in time to allow a socket to send more packets.

For say a UDP server, it would be quite mandatory, as it usually uses a
single UDP socket to receive and send messages.





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