Messages in this thread Patch in this message | | | From | Rusty Russell <> | Subject | Re: [PATCH] modules: Take a shortcut for checking if an address is in a module | Date | Thu, 26 Jun 2008 15:46:58 +1000 |
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On Thursday 12 June 2008 10:20:58 Rusty Russell wrote: > Or, we could actually make those as variables and update them in module.c > itself. No arch changes required, and pretty easy to understand.
And since you didn't reply, here's the patch.
modules: Take a shortcut for checking if an address is in a module
This patch keeps track of the boundaries of module allocation, in order to speed up module_text_address().
Inspired by Arjan's version, which required arch-specific defines:
Various pieces of the kernel (lockdep, latencytop, etc) tend to store backtraces, sometimes at a relatively high frequency. In itself this isn't a big performance deal (after all you're using diagnostics features), but there have been some complaints from people who have over 100 modules loaded that this is a tad too slow.
This is due to the new backtracer code which looks at every slot on the stack to see if it's a kernel/module text address, so that's 1024 slots. 1024 times 100 modules... that's a lot of list walking.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au> --- kernel/module.c | 24 ++++++++++++++++++++++-- 1 file changed, 22 insertions(+), 2 deletions(-)
diff --git a/kernel/module.c b/kernel/module.c --- a/kernel/module.c +++ b/kernel/module.c @@ -69,6 +69,9 @@ static DECLARE_WAIT_QUEUE_HEAD(module_wq static DECLARE_WAIT_QUEUE_HEAD(module_wq); static BLOCKING_NOTIFIER_HEAD(module_notify_list); + +/* Bounds of module allocation, for speeding __module_text_address */ +static unsigned long module_addr_min = -1UL, module_addr_max = 0; int register_module_notifier(struct notifier_block * nb) { @@ -1770,6 +1773,20 @@ static inline void add_kallsyms(struct m } #endif /* CONFIG_KALLSYMS */ +static void *module_alloc_update_bounds(unsigned long size) +{ + void *ret = module_alloc(size); + + if (ret) { + /* Update module bounds. */ + if ((unsigned long)ret < module_addr_min) + module_addr_min = (unsigned long)ret; + if ((unsigned long)ret + size > module_addr_max) + module_addr_max = (unsigned long)ret + size; + } + return ret; +} + /* Allocate and load the module: note that size of section 0 is always zero, and we rely on this for optional sections. */ static struct module *load_module(void __user *umod, @@ -1971,7 +1988,7 @@ static struct module *load_module(void _ layout_sections(mod, hdr, sechdrs, secstrings); /* Do the allocs. */ - ptr = module_alloc(mod->core_size); + ptr = module_alloc_update_bounds(mod->core_size); if (!ptr) { err = -ENOMEM; goto free_percpu; @@ -1979,7 +1996,7 @@ static struct module *load_module(void _ memset(ptr, 0, mod->core_size); mod->module_core = ptr; - ptr = module_alloc(mod->init_size); + ptr = module_alloc_update_bounds(mod->init_size); if (!ptr && mod->init_size) { err = -ENOMEM; goto free_core; @@ -2636,6 +2653,9 @@ struct module *__module_text_address(uns { struct module *mod; + if (addr < module_addr_min || addr > module_addr_max) + return NULL; + list_for_each_entry(mod, &modules, list) if (within(addr, mod->module_init, mod->init_text_size) || within(addr, mod->module_core, mod->core_text_size))
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