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Date: Mon, 21 Dec 2009 16:59:36 +0900 From: Tejun Heo <tj@...nel.org> To: Christoph Lameter <cl@...ux-foundation.org> CC: linux-kernel@...r.kernel.org, Mel Gorman <mel@....ul.ie>, Pekka Enberg <penberg@...helsinki.fi>, Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>, Rusty Russell <rusty@...tcorp.com.au> Subject: Re: [this_cpu_xx V8 07/16] Module handling: Use this_cpu_xx to dynamically allocate counters Here's the version I committed to percpu branch. Thanks. >From 8af47ddd01364ae3c663c0bc92415c06fe887ba1 Mon Sep 17 00:00:00 2001 From: Christoph Lameter <cl@...ux-foundation.org> Date: Fri, 18 Dec 2009 16:26:24 -0600 Subject: [PATCH] module: Use this_cpu_xx to dynamically allocate counters Use cpu ops to deal with the per cpu data instead of a local_t. Reduces memory requirements, cache footprint and decreases cycle counts. The this_cpu_xx operations are also used for !SMP mode. Otherwise we could not drop the use of __module_ref_addr() which would make per cpu data handling complicated. this_cpu_xx operations have their own fallback for !SMP. The last hold out of users of local_t is the tracing ringbuffer after this patch has been applied. Signed-off-by: Christoph Lameter <cl@...ux-foundation.org> Cc: Rusty Russell <rusty@...tcorp.com.au> Signed-off-by: Tejun Heo <tj@...nel.org> --- include/linux/module.h | 38 ++++++++++++++------------------------ kernel/module.c | 30 ++++++++++++++++-------------- 2 files changed, 30 insertions(+), 38 deletions(-) diff --git a/include/linux/module.h b/include/linux/module.h index 482efc8..9350577 100644 --- a/include/linux/module.h +++ b/include/linux/module.h @@ -16,8 +16,7 @@ #include <linux/kobject.h> #include <linux/moduleparam.h> #include <linux/tracepoint.h> - -#include <asm/local.h> +#include <linux/percpu.h> #include <asm/module.h> #include <trace/events/module.h> @@ -361,11 +360,9 @@ struct module /* Destruction function. */ void (*exit)(void); -#ifdef CONFIG_SMP - char *refptr; -#else - local_t ref; -#endif + struct module_ref { + int count; + } *refptr; #endif #ifdef CONFIG_CONSTRUCTORS @@ -452,25 +449,16 @@ void __symbol_put(const char *symbol); #define symbol_put(x) __symbol_put(MODULE_SYMBOL_PREFIX #x) void symbol_put_addr(void *addr); -static inline local_t *__module_ref_addr(struct module *mod, int cpu) -{ -#ifdef CONFIG_SMP - return (local_t *) (mod->refptr + per_cpu_offset(cpu)); -#else - return &mod->ref; -#endif -} - /* Sometimes we know we already have a refcount, and it's easier not to handle the error case (which only happens with rmmod --wait). */ static inline void __module_get(struct module *module) { if (module) { - unsigned int cpu = get_cpu(); - local_inc(__module_ref_addr(module, cpu)); + preempt_disable(); + __this_cpu_inc(module->refptr->count); trace_module_get(module, _THIS_IP_, - local_read(__module_ref_addr(module, cpu))); - put_cpu(); + __this_cpu_read(module->refptr->count)); + preempt_enable(); } } @@ -479,15 +467,17 @@ static inline int try_module_get(struct module *module) int ret = 1; if (module) { - unsigned int cpu = get_cpu(); + preempt_disable(); + if (likely(module_is_live(module))) { - local_inc(__module_ref_addr(module, cpu)); + __this_cpu_inc(module->refptr->count); trace_module_get(module, _THIS_IP_, - local_read(__module_ref_addr(module, cpu))); + __this_cpu_read(module->refptr->count)); } else ret = 0; - put_cpu(); + + preempt_enable(); } return ret; } diff --git a/kernel/module.c b/kernel/module.c index 64787cd..9bc04de 100644 --- a/kernel/module.c +++ b/kernel/module.c @@ -474,9 +474,10 @@ static void module_unload_init(struct module *mod) INIT_LIST_HEAD(&mod->modules_which_use_me); for_each_possible_cpu(cpu) - local_set(__module_ref_addr(mod, cpu), 0); + per_cpu_ptr(mod->refptr, cpu)->count = 0; + /* Hold reference count during initialization. */ - local_set(__module_ref_addr(mod, raw_smp_processor_id()), 1); + __this_cpu_write(mod->refptr->count, 1); /* Backwards compatibility macros put refcount during init. */ mod->waiter = current; } @@ -555,6 +556,7 @@ static void module_unload_free(struct module *mod) kfree(use); sysfs_remove_link(i->holders_dir, mod->name); /* There can be at most one match. */ + free_percpu(i->refptr); break; } } @@ -619,7 +621,7 @@ unsigned int module_refcount(struct module *mod) int cpu; for_each_possible_cpu(cpu) - total += local_read(__module_ref_addr(mod, cpu)); + total += per_cpu_ptr(mod->refptr, cpu)->count; return total; } EXPORT_SYMBOL(module_refcount); @@ -796,14 +798,15 @@ static struct module_attribute refcnt = { void module_put(struct module *module) { if (module) { - unsigned int cpu = get_cpu(); - local_dec(__module_ref_addr(module, cpu)); + preempt_disable(); + __this_cpu_dec(module->refptr->count); + trace_module_put(module, _RET_IP_, - local_read(__module_ref_addr(module, cpu))); + __this_cpu_read(module->refptr->count)); /* Maybe they're waiting for us to drop reference? */ if (unlikely(!module_is_live(module))) wake_up_process(module->waiter); - put_cpu(); + preempt_enable(); } } EXPORT_SYMBOL(module_put); @@ -1377,9 +1380,9 @@ static void free_module(struct module *mod) kfree(mod->args); if (mod->percpu) percpu_modfree(mod->percpu); -#if defined(CONFIG_MODULE_UNLOAD) && defined(CONFIG_SMP) +#if defined(CONFIG_MODULE_UNLOAD) if (mod->refptr) - percpu_modfree(mod->refptr); + free_percpu(mod->refptr); #endif /* Free lock-classes: */ lockdep_free_key_range(mod->module_core, mod->core_size); @@ -2145,9 +2148,8 @@ static noinline struct module *load_module(void __user *umod, mod = (void *)sechdrs[modindex].sh_addr; kmemleak_load_module(mod, hdr, sechdrs, secstrings); -#if defined(CONFIG_MODULE_UNLOAD) && defined(CONFIG_SMP) - mod->refptr = percpu_modalloc(sizeof(local_t), __alignof__(local_t), - mod->name); +#if defined(CONFIG_MODULE_UNLOAD) + mod->refptr = alloc_percpu(struct module_ref); if (!mod->refptr) { err = -ENOMEM; goto free_init; @@ -2373,8 +2375,8 @@ static noinline struct module *load_module(void __user *umod, kobject_put(&mod->mkobj.kobj); free_unload: module_unload_free(mod); -#if defined(CONFIG_MODULE_UNLOAD) && defined(CONFIG_SMP) - percpu_modfree(mod->refptr); +#if defined(CONFIG_MODULE_UNLOAD) + free_percpu(mod->refptr); free_init: #endif module_free(mod, mod->module_init); -- 1.6.4.2 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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