On Wednesday 12 April 2006 20:18, Dave Dillow wrote: > > > or loaded. And even if it saves 200 bytes in one > > > module, unless that module text was already less than 200 bytes into a > > > page, you've saved no memory -- a 4300 byte module takes 2 pages on x86, > > > as does a 4100 byte module. > > > > Sometimes, those 200 bytes can bring module size just under 4096. > > Thus on the average, on many modules you get the same size savings > > as on built-in code. (Not that we have THAT many network modules...) > > You're making a bogus leap from "sometimes" to "average".
It's not bogus. See below. > Assuming an even distribution of lengths mod 4096, less than 5% of the > time will 200 bytes save any memory on a module. Ok, imagine perfect module size distribution, and suppose we shave 204 bytes off each module. 5% of the modules will have their size reduced so that they occupy one 4k page less. Those 5% of modules will have their RAM footprint reduced not by just 204 bytes, but by 4096 bytes. Total RAM footprint of all modules, in kb (N=number of modules): before: sum_of_orig_module_size after, modular: sum_of_orig_module_size - 0.05*N * 4096 after, builtin: sum_of_orig_module_size - N * 204 0.05*4096 = 204.53 > I don't like "VLAN_ENABLED" as a global define -- it looks too much like > something local. The CONFIG_VLAN... defines were more descriptive. That will require Kconfig changes. Maybe you would like "VLAN_ENABLED_KERNER" name? It doesn't sound local... > I didn't think about this before, but I'm pretty sure you're taking away > functionality. When I wrote the typhoon driver, ISTR that I looked > through the vlan implantation, and determined that all the #ifdefs on > CONFIG_VLAN_8021Q were not really needed, since all the hooks were > there. You could just load the 8021q module (even perhaps building it at > a later date), and it would work if you had filled in the hooks in > struct net_device. So I didn't #ifdef out code in my driver to let the > user have the option. IOW: currently most of VLAN code is already in kernel. Then why do we have VLAN as a config option? Let's make it unconditional (will add only 10k to core kernel)? # size net/8021q/8021q.o text data bss dec hex filename 9379 484 136 9999 270f net/8021q/8021q.o > You're taking that away in the name of a total of 5K, which most users > won't actually get back? It started as a kernel-wide audit for huge inlines, I was not aiming at VLAN particularly. But yes, when I saw other (not related to inlines) opportunities to make code smaller, I decided to do it. You know, people say that even Linux is getting fat these days. -- vda - To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
