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SubjectRe: delayed acks after fast recover
   Date: Mon, 30 Nov 1998 20:44:25 +0100 (CET)
From: Andrea Arcangeli <>

>One problem I have so far though:
>@@ -129,7 +166,7 @@
> tp->delayed_acks++;
> /* Tiny-grams with PSH set make us ACK quickly. */
> if(th->psh && (skb->len < (tp->mss_cache >> 1)))
>- tp->ato = HZ/50;
>+ tp->delack_mode |= TCP_DELACK_DISABLE;
> }
> /* Called to compute a smoothed rtt estimate. The data fed to this
>This is wrong, I don't like this. The code wants to ack "quickly" not
>"right now" in these cases. There is an example case I once saw in a

quickly == right now over my ppp link ;).

Over your ppp link, right now vs. HZ/50 won't make one single difference.

Probably is better to remove the whole check for pushed little
segments if you care to decrease the network load.

It doesn't work like that. There are many cases where this heuristic
improves responsiveness substantially and many people cried before I
put it in (2.0.x does something like this too).

David S. Miller

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