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RE: [PATCH 2.6.12-rc4] IPv4/IPv6: UDP Large Send Offload feature

To: "'David S. Miller'" <davem@xxxxxxxxxxxxx>
Subject: RE: [PATCH 2.6.12-rc4] IPv4/IPv6: UDP Large Send Offload feature
From: "Ravinandan Arakali" <ravinandan.arakali@xxxxxxxxxxxx>
Date: Fri, 27 May 2005 09:32:00 -0700
Cc: <jgarzik@xxxxxxxxx>, <netdev@xxxxxxxxxxx>, <raghavendra.koushik@xxxxxxxxxxxx>, <leonid.grossman@xxxxxxxxxxxx>, <ananda.raju@xxxxxxxxxxxx>, <rapuru.sriram@xxxxxxxxxxxx>
Importance: Normal
In-reply-to: <20050526.164217.45745005.davem@xxxxxxxxxxxxx>
Sender: netdev-bounce@xxxxxxxxxxx
Hi David,
Thanks for the quick feedback.
At that time when we considered using skb_shinfo(skb)->fraglist,
it contained fragments of MTU size. So, for a 60k udp datagram 
and 1500 MTU we will have 60k/1500 = 45 fragments which is
more than MAX_SKB_FRAGS(18).

However we will relook at fraglist for the possibility of increasing
frag size to >MTU.

Thanks,
Ravi 

-----Original Message-----
From: David S. Miller [mailto:davem@xxxxxxxxxxxxx]
Sent: Thursday, May 26, 2005 4:42 PM
To: ravinandan.arakali@xxxxxxxxxxxx
Cc: jgarzik@xxxxxxxxx; netdev@xxxxxxxxxxx;
raghavendra.koushik@xxxxxxxxxxxx; leonid.grossman@xxxxxxxxxxxx;
ananda.raju@xxxxxxxxxxxx; rapuru.sriram@xxxxxxxxxxxx
Subject: Re: [PATCH 2.6.12-rc4] IPv4/IPv6: UDP Large Send Offload
feature



sock_append_data() seems like a lot of wasted work.

We already pass around the fragmented SKB as a list chained by
skb_shinfo(skb)->fraglist, just pass this thing to the device and in
this way you'll avoid all of that work sock_append_data() does
entirely.

Or is there a reason you did not implement it this
way?

This is one of the uses the skb_shinfo(skb)->fraglist was intended
for.

IN FACT, this fragmentation offload you are implementing here is what
the feature bit NETIF_F_FRAGLIST was meant to indicate.


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