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Re: issue with new TCP TSO stuff

To: ak@xxxxxx
Subject: Re: issue with new TCP TSO stuff
From: "David S. Miller" <davem@xxxxxxxxxxxxx>
Date: Thu, 12 May 2005 12:26:57 -0700 (PDT)
Cc: netdev@xxxxxxxxxxx
In-reply-to: <m1sm0sttvy.fsf@xxxxxx>
References: <20050511.223036.39664020.davem@xxxxxxxxxxxxx> <m1sm0sttvy.fsf@xxxxxx>
Sender: netdev-bounce@xxxxxxxxxxx
From: Andi Kleen <ak@xxxxxx>
Subject: Re: issue with new TCP TSO stuff
Date: Thu, 12 May 2005 16:13:05 +0200

> Are you sure a few atomic_inc/dec are really causing noticeable
> slowdown? That would surprise me unless you have lots of cache line
> bouncing on a MP system.

It's about 7 or 8 times as many atomic gets and puts on pages compared
to the older code (with an 8K page size).

Some of it we can't get rid of, because we keep a normal write queue
segmented set of SKBs around.

But the TSO part we can eliminate.

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