Re: Linux 2.2.2 TCP delays every 41st small packet by 10-20 ms

David Miller (davem@twiddle.net)
Fri, 26 Feb 1999 11:27:47 -0800


Date: Fri, 26 Feb 1999 18:18:25 +0100 (CET)
From: Andrea Arcangeli <andrea@e-mind.com>

On Thu, 25 Feb 1999, Josip Loncaric wrote:

>The conclusion is this: in Linux TCP, every N-th small packet is delayed
>by 1-2 "jiffies" (defined by the 100 Hz system clock). For Linux kernel

This 1-2 jiffies made me thing again at the PSH thing. Probably I am
completly out but could you try this patch?

Two things (and no I have nothing against people testing this patch,
it's very useful to see what the traces look like with this change):

1) From my look at the traces involved, NT should not be sending 1
packet each of these intervals after the first DATA-->ACK, it
should get in at least two for each further ACK, it is not.
I want to find the real problem.

2) Even if your fix was to be the final one, we have to be careful,
as just blindly ACK'ing immediately for small PSH packets is
deadly and will kill Nagle immediately. Actually the effect is
that nobody will be able to successfully perform Nagle to us.

Later,
David S. Miller
davem@redhat.com


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