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Re: bad TSO performance in 2.6.9-rc2-BK

To: "David S. Miller" <davem@xxxxxxxxxxxxx>
Subject: Re: bad TSO performance in 2.6.9-rc2-BK
From: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>
Date: Mon, 27 Sep 2004 15:45:41 +1000
Cc: ak@xxxxxxx, niv@xxxxxxxxxx, andy.grover@xxxxxxxxx, anton@xxxxxxxxx, netdev@xxxxxxxxxxx
In-reply-to: <20040926210029.22750d47.davem@xxxxxxxxxxxxx>
References: <20040923164149.5368d291.davem@xxxxxxxxxxxxx> <E1CBkIW-0001dF-00@xxxxxxxxxxxxxxxxxxxxxxxx> <20040927025048.GA6723@xxxxxxxxxxxxxxxxxxx> <20040926210029.22750d47.davem@xxxxxxxxxxxxx>
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On Sun, Sep 26, 2004 at 09:00:29PM -0700, David S. Miller wrote:
> 
> The very next time we check to see if we can
> make forward progress on the send queue we'll call tcp_current_mss()
> which causes the right things to happen.

tcp_current_mss() doesn't call tcp_sync_mss() unless the PMTU changes.

> Something else is wrong.  I think part of it is that we need to
> make tcp_clean_rtx_queue() return FLAG_DATA_ACKED even when a
> partial TSO packet is ACK'd by the other end.  This will make
> RTO etc. calculations actually occur, among other things.  But
> I have no idea if that will clear up the performance problems
> TSO is having with the new code.

There probably is something else wrong, since this should only limit
the TSO size.
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