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Message-ID: <20160419172837.GA37697@kafai-mba.local> Date: Tue, 19 Apr 2016 10:28:37 -0700 From: Martin KaFai Lau <kafai@...com> To: Soheil Hassas Yeganeh <soheil@...gle.com> CC: <netdev@...r.kernel.org>, Eric Dumazet <edumazet@...gle.com>, Neal Cardwell <ncardwell@...gle.com>, Soheil Hassas Yeganeh <soheil.kdev@...il.com>, Willem de Bruijn <willemb@...gle.com>, Yuchung Cheng <ycheng@...gle.com>, Kernel Team <kernel-team@...com> Subject: Re: [RFC PATCH v2 net-next 2/7] tcp: Merge tx_flags/tskey/txstamp_ack in tcp_collapse_retrans On Tue, Apr 19, 2016 at 01:32:14AM -0400, Soheil Hassas Yeganeh wrote: > > + TCP_SKB_CB(skb)->txstamp_ack = > > + !!(shinfo->tx_flags & SKBTX_ACK_TSTAMP); > > Maybe we can skip a conditional jump here (because of !!), by simply > using the cached bit in next_skb: > TCP_SKB_CB(skb)->txstamp_ack = TCP_SKB_CB(next_skb)->txstamp_ack; Recall the tx_flags are merged/combined (and so should be the txstamp_ack). Would there be a case that TCP_SKB_CB(skb)->txstamp_ack is 1 and TCP_SKB_CB(next_skb)->txstamp_ack is 0? I can change it like the following which may help in showing the intention: if (TCP_SKB_CB(next_skb)->txstamp_ack) TCP_SKB_CB(skb)->txstamp_ack = 1; A bit off topic, I feel like the SKBTX_ACK_TSTAMP and txstamp_ack are sort of redundant but I have not look into the details yet, so not completely sure. It wwould be a separate cleanup patch if it is the case.
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