netdev - Re: [PATCH v2 net-next 2/2] tcp: remove SKBTX_ACK

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Message-ID: <1461818255.5535.89.camel@edumazet-glaptop3.roam.corp.google.com>
Date:	Wed, 27 Apr 2016 21:37:35 -0700
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Soheil Hassas Yeganeh <soheil.kdev@...il.com>
Cc:	davem@...emloft.net, netdev@...r.kernel.org, kafai@...com,
	willemb@...gle.com, edumazet@...gle.com, ycheng@...gle.com,
	ncardwell@...gle.com, Soheil Hassas Yeganeh <soheil@...gle.com>
Subject: Re: [PATCH v2 net-next 2/2] tcp: remove SKBTX_ACK_TSTAMP since it
 is redundant

On Wed, 2016-04-27 at 23:39 -0400, Soheil Hassas Yeganeh wrote:
> From: Soheil Hassas Yeganeh <soheil@...gle.com>
> 
> The SKBTX_ACK_TSTAMP flag is set in skb_shinfo->tx_flags when
> the timestamp of the TCP acknowledgement should be reported on
> error queue. Since accessing skb_shinfo is likely to incur a
> cache-line miss at the time of receiving the ack, the
> txstamp_ack bit was added in tcp_skb_cb, which is set iff
> the SKBTX_ACK_TSTAMP flag is set for an skb. This makes
> SKBTX_ACK_TSTAMP flag redundant.
> 
> Remove the SKBTX_ACK_TSTAMP and instead use the txstamp_ack bit
> everywhere.
> 
> Note that this frees one bit in shinfo->tx_flags.
> 
> Signed-off-by: Soheil Hassas Yeganeh <soheil@...gle.com>
> Acked-by: Martin KaFai Lau <kafai@...com>
> Suggested-by: Willem de Bruijn <willemb@...gle.com>
> ---

Acked-by: Eric Dumazet <edumazet@...gle.com>