tcp: remove SKBTX_ACK_TSTAMP since it is redundant
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: NSoheil Hassas Yeganeh <soheil@google.com> Acked-by: NMartin KaFai Lau <kafai@fb.com> Suggested-by: NWillem de Bruijn <willemb@google.com> Acked-by: NEric Dumazet <edumazet@google.com> Signed-off-by: NDavid S. Miller <davem@davemloft.net>
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