Messages in this thread |  | | Subject | NETIF_F_(SG|FRAGLIST|HIGHDMA) docs anywhere? | From | Daniel Stodden <> | Date | 29 Dec 2001 08:16:12 +0100 |
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hi.
software-only network device, currently implementing none of the dev->features flags.
the driver transmits packets via pci dma to other processors residing on a shared PCI bus segment. so i guess supporting at least scatter/gather should give some performance improvements in order to get rid of skb_linearize() on xmit? since transmission is done completely by the local cpu, all of F_SG/FRAGLIST/HIGHDMA look relatively easy to implemement to me.
my major problem is test cases and getting the picture behind these structures. is there any documentation around on the skb_shinfo(skb)->frags and skb_shinfo(skb)->frag_list stuff? i've spend quite some time now trying to figure out exactly under which circumstances which of both applies. not too successful i must admit :)
frag_list seems to be the list involved with keeping track of ip fragmentation. so dev->hard_start_xmit() with frag_list set would only happen on routers or when??
when is nr_frags>0? i've found some postings indicating sendfile(2) will benefit here. is this the only case? need some test code..
any hint appreciated, dns
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