[Freeciv-Dev] server i/o patch

[Vasco Alexandre Da Silva Costa <vasc@xxxxxxxxxxxxxx>]

I've been running a couple of tests to see what's the main cause for
server-->client network traffic in the game.  The result of a couple of
these tests is attached with this mail.

(tested with default map size, generator 2, 4 AIs)

In short, the tests show the main causes for network traffic are:
PACKET_UNIT_INFO, PACKET_CITY_INFO and PACKET_TILE_INFO.

The minimum size for the contents of each of these packets is:
PACKET_UNIT_INFO:       2+4*1+2+11*1+2          = 21 bytes
PACKET_CITY_INFO:       2+3*1+?+9*1+10*2+1+1+1  > 37 bytes
PACKET_TILE_INFO:       3*1+2+1                 = 6 bytes

(add to the figures above 2 bytes for the length field, and another
byte for the packet type field).

Since the tile packets are already highly optimized (actually they aren't 
but the other two are MUCH worse), we should try to optimize the server to
send less redundant unit & city data.  Some things could be improved:

=== PACKET_UNIT_INFO:

* maybe some things like upkeep could be calculated by the client to save
  sending that info?
* some info doesn't change often (eg: homecity, upkeep, upkeep_food, 
  upkeep_gold), or never changes (type).  so shouldn't be always sent.
* goto data is being always sent even if the unit isn't on goto mode.

=== PACKET_CITY_INFO:

* again, some info doesn't change often (city name, trade data), or
  never changes (x, y).
* not all data is required sometimes (eg: if you are receiving info on
  enemy cities not covered by FoW).


Also attached is a newer version of the net patch that adds dynamic
send buffers, and some other minor fixes.  I didn't have the time to merge
Lauri's latest changes yet.

---
Vasco Alexandre da Silva Costa @ Instituto Superior Tecnico, Lisboa

test2.log.gz
Description: Binary data

test3.log.gz
Description: Binary data

freeciv-net-2.1.patch.gz
Description: Binary data