Enable /proc/config.gz, use -O2 instead of -Os

[ThomasKaiser]

Could you please add

CONFIG_IKCONFIG=y CONFIG_IKCONFIG_PROC=y

to your default kernel config and also consider disabling CONFIG_CC_OPTIMIZE_FOR_SIZE -- improved network and USB throughput in my tests and is also disabled on other ARM OS images for a reason. Please compare also with http://www.phoronix.com/forums/forum/phoronix/phoronix-test-suite/16049-linux-config_cc_optimize_for_size?p=179158#post179158