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Re: zerocopy changes in 3c59x.c

To: "David S. Miller" <davem@xxxxxxxxxx>
Subject: Re: zerocopy changes in 3c59x.c
From: Andrew Morton <andrewm@xxxxxxxxxx>
Date: Sat, 27 Jan 2001 00:27:32 +1100
Cc: Alexey Kuznetsov <kuznet@xxxxxxxxxxxxx>, "netdev@xxxxxxxxxxx" <netdev@xxxxxxxxxxx>
References: <3A716447.CF6E8BB0@xxxxxxxxxx>, <3A714788.82C064BD@xxxxxxxxxx> <14961.24733.869800.77633@xxxxxxxxxxxxxxx> <3A716447.CF6E8BB0@xxxxxxxxxx> <14961.30181.671982.174763@xxxxxxxxxxxxxxx>
Sender: owner-netdev@xxxxxxxxxxx
"David S. Miller" wrote:
> 
> Andrew Morton writes:
>  > But why do this, rather than create new accounting fields?  Let
>  > me guess: short-term thing, intended to be removed, didn't want
>  > to hack the userspace tools?
> 
> Why add new fields when they are unnecessary?  What is hurt
> by having these fields increment.
> 

Hey, I was just asking!  Dunno about others, but for me
the zc thing has basically come from nowhere - I'm still
coming up to speed about the design decisions which were
made, how it is implemented, etc.

/proc/net/dev says:

Inter-|   Receive                                                |  Transmit
 face |bytes    packets errs drop fifo frame compressed multicast|bytes    
packets errs drop fifo colls carrier compressed
    lo:       0       0    0    0    0     0          0         0        0      
 0    0    0    0     0       0          0
  eth0:   14274     104    0    0    0     0         54         0     5414      
69    0    0    0     0       0         54

So this:                                             ^^

tells us that 54 packets have been sent with h/w checksums and this:            
                                        ^^

tells us that they were all multi-fragment.

I assume this is because the IP header is in a different frag?

Is there ever a situation in which these numbers will differ?

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