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

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Message-ID: <1423580974.28434.29.camel@edumazet-glaptop2.roam.corp.google.com>
Date:	Tue, 10 Feb 2015 07:09:34 -0800
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Johannes Berg <johannes@...solutions.net>
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>,
	Eyal Perry <eyalpe@....mellanox.co.il>
Subject: Re: Throughput regression with `tcp: refine TSO autosizing`

On Tue, 2015-02-10 at 15:19 +0100, Johannes Berg wrote:
> On Tue, 2015-02-10 at 11:33 +0100, Michal Kazior wrote:
> 
> > +       if (msdu->sk) {
> > +               ewma_add(&ar->tx_delay_us,
> > +                        ktime_to_ns(ktime_sub(ktime_get(), skb_cb->stamp)) /
> > +                        NSEC_PER_USEC);
> > +
> > +               ACCESS_ONCE(msdu->sk->sk_tx_completion_delay_cushion) =
> > +                               (ewma_read(&ar->tx_delay_us) *
> > +                                msdu->sk->sk_pacing_rate) >> 20;
> > +       }
> 
> To some extent, every wifi driver is going to have this problem. Perhaps
> we should do this in mac80211?

I'll provide the TCP patch.

sk->sk_tx_completion_delay_cushion is probably a wrong name, as the
units here are in bytes, since it is really number of bytes in the
network driver that accommodate for tx completions delays. 

tx_completion_delay * pacing_rate

sk_tx_completion_cushion maybe.


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