I Got lot of comments on the book saying that the book is not up-to-date. This is partially correct and it is all in the mind. I have myself looked into 2.6 latest networking kernel related to TCP/IP. I found that except for the few features, major algorithms remain the same. If I take route lookup algorithm, I really don't see any. So, performance as far as route lookup is concerned should not vary much as data-structure remains the same for the routing table and Linux still implements hashtable. If I see major difference, it lies in the locking mechanism for the routing caches.
Instead of using read spin locks, we now use RCU locks(read-copy-update). This will get big gain in the route cache lookup performance, when huge route lookups are performed on the SMP Linux machine.
ip_route_output_key() takes additional argument 'struct flowi' and so also ip_route_output_slow(). In 2.4.x 'struct rt_key' is used instead for searching. struct flowi is more comprehensive search key to find more perfect match for a given flow for e.g., sourrce/destination port numbers.
This is one of the major difference but updting base routing table FIB, has not changed and has no performance gain in searching/inserting/deleting entry from here.
Another area where I see major difference is the socket data-structure. Once again the changes have got nothing much to do with performance. It is just better organization of the socket structure for better code readability. Following macros are used to access protocol specific socket information from 'struct sock' -
inet_sk() for getting pointer to inet protocol family.
udp/tcp_sk() for getting udp/tcp protocol specific socket pointer. This will map original 'struct sock' to struct tcp/udp_sock.
Entire description can't go here as it requires big space. But, I'll keep updating the entries, whereever I find major differences that can be explained in short. If we know the baisc skeleton and terminology of the Linux networking kernel, it will be easy to understand the most recent code and reason it out.
I'm working on next revision where I'm putting all the details related to the differences and much more........!!!!
Instead of using read spin locks, we now use RCU locks(read-copy-update). This will get big gain in the route cache lookup performance, when huge route lookups are performed on the SMP Linux machine.
ip_route_output_key() takes additional argument 'struct flowi' and so also ip_route_output_slow(). In 2.4.x 'struct rt_key' is used instead for searching. struct flowi is more comprehensive search key to find more perfect match for a given flow for e.g., sourrce/destination port numbers.
This is one of the major difference but updting base routing table FIB, has not changed and has no performance gain in searching/inserting/deleting entry from here.
Another area where I see major difference is the socket data-structure. Once again the changes have got nothing much to do with performance. It is just better organization of the socket structure for better code readability. Following macros are used to access protocol specific socket information from 'struct sock' -
inet_sk() for getting pointer to inet protocol family.
udp/tcp_sk() for getting udp/tcp protocol specific socket pointer. This will map original 'struct sock' to struct tcp/udp_sock.
Entire description can't go here as it requires big space. But, I'll keep updating the entries, whereever I find major differences that can be explained in short. If we know the baisc skeleton and terminology of the Linux networking kernel, it will be easy to understand the most recent code and reason it out.
I'm working on next revision where I'm putting all the details related to the differences and much more........!!!!
