Messages in this thread | | | Date | Sat, 9 Feb 2008 22:27:18 -0200 | From | Arnaldo Carvalho de Melo <> | Subject | Re: [RFC] Sectionized printk data |
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Em Sun, Feb 10, 2008 at 01:18:18AM +0100, Jan Engelhardt escreveu: > > On Feb 9 2008 21:54, Arnaldo Carvalho de Melo wrote: > >> To drop strings that are only shown once anyway, such as: > >> > >> static int __init ebtables_init(void) > >> { > >> int ret; > >> > >> mutex_lock(&ebt_mutex); > >> list_add(&ebt_standard_target.list, &ebt_targets); > >> mutex_unlock(&ebt_mutex); > >> if ((ret = nf_register_sockopt(&ebt_sockopts)) < 0) > >> return ret; > >> > >> -> printk(KERN_INFO "Ebtables v2.0 registered\n"); > >> return 0; > >> } > >> > >> >If you say "saving memory" then please let us know with specific examples > >> >in what area these savings will really pay off. > > > >[...] > >With a tool like this the advantage is that no source code has to be > >changed, strings in __init functions are automagically moved to > >.init.data, the disadvantage is that not all strings can be moved to > >.init.data as there were (are?) subsystems that keep pointers to the > >string passed and another tool would be involved in the build process. > > There is one corner case to consider: > > > static char abc[] = "foo"; > > int __init init_module(void) > { > printk(abc); > } > > I am not sure if gcc/ld is smart enough to figure out that abc is > only ever used from within an __init function and that it could hence > be moved to __initdata.
The initstr tool mentioned doesn't touches this case, as it doesn't searches specific functions such as printk, it looks for strings inside __init marked functions. In the above example abc won't be marked as __initdata.
So if there are two places where the same string is used, with one being in a __init function one copy goes to .init.data and another to .data.
- Arnaldo
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