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    SubjectRe: [RFC][PATCH] tracing/module: Move tracepoint out of module.h
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    On Thu, 2012-01-26 at 11:28 +0100, Ingo Molnar wrote:

    > How much more do we save if we move all of try_module_get() out
    > of line? It still seems a rather thick inline function with
    > preempt section and all. I'd *really* suggest that it should all
    > be uninlined.
    >

    Here's the #'s

    text data bss dec hex filename
    7489488 2249584 9719808 19458880 128eb40 vmlinux-prepatch
    text data bss dec hex filename
    7482458 2248048 9719808 19450314 128c9ca vmlinux-postpatch
    text data bss dec hex filename
    7477393 2248080 9719808 19445281 128b621 vmlinux-updatedpatch

    Thus we get an additional 5k it seems, for a total of 13k savings.

    The below patch is what I used. Note, since the tracepoint requires the
    instruction pointer, I created stub versions that call a "do_" version
    of the function to pass in the local instruction counter.

    Rusty, can you give your acked-by on that patch?

    Thanks!

    -- Steve

    diff --git a/include/linux/module.h b/include/linux/module.h
    index 3cb7839..2337f97 100644
    --- a/include/linux/module.h
    +++ b/include/linux/module.h
    @@ -21,8 +21,6 @@
    #include <linux/percpu.h>
    #include <asm/module.h>

    -#include <trace/events/module.h>
    -
    /* Not Yet Implemented */
    #define MODULE_SUPPORTED_DEVICE(name)

    @@ -439,34 +437,17 @@ void __symbol_put(const char *symbol);
    #define symbol_put(x) __symbol_put(MODULE_SYMBOL_PREFIX #x)
    void symbol_put_addr(void *addr);

    -/* Sometimes we know we already have a refcount, and it's easier not
    - to handle the error case (which only happens with rmmod --wait). */
    +extern void do_module_get(struct module *module, int ip);
    +extern int do_try_module_get(struct module *module, int ip);
    +
    static inline void __module_get(struct module *module)
    {
    - if (module) {
    - preempt_disable();
    - __this_cpu_inc(module->refptr->incs);
    - trace_module_get(module, _THIS_IP_);
    - preempt_enable();
    - }
    + do_module_get(module, _THIS_IP_);
    }

    static inline int try_module_get(struct module *module)
    {
    - int ret = 1;
    -
    - if (module) {
    - preempt_disable();
    -
    - if (likely(module_is_live(module))) {
    - __this_cpu_inc(module->refptr->incs);
    - trace_module_get(module, _THIS_IP_);
    - } else
    - ret = 0;
    -
    - preempt_enable();
    - }
    - return ret;
    + return do_try_module_get(module, _THIS_IP_);
    }

    extern void module_put(struct module *module);
    diff --git a/kernel/module.c b/kernel/module.c
    index 178333c..8955199 100644
    --- a/kernel/module.c
    +++ b/kernel/module.c
    @@ -928,6 +928,42 @@ void module_put(struct module *module)
    }
    EXPORT_SYMBOL(module_put);

    +static void inc_module(struct module *module, unsigned long ip)
    +{
    + __this_cpu_inc(module->refptr->incs);
    + trace_module_get(module, ip);
    +}
    +
    +/* Sometimes we know we already have a refcount, and it's easier not
    + to handle the error case (which only happens with rmmod --wait). */
    +void do_module_get(struct module *module, int ip)
    +{
    + if (module) {
    + preempt_disable();
    + inc_module(module, ip);
    + preempt_enable();
    + }
    +}
    +EXPORT_SYMBOL(do_module_get);
    +
    +int do_try_module_get(struct module *module, int ip)
    +{
    + int ret = 1;
    +
    + if (module) {
    + preempt_disable();
    +
    + if (likely(module_is_live(module)))
    + inc_module(module, ip);
    + else
    + ret = 0;
    +
    + preempt_enable();
    + }
    + return ret;
    +}
    +EXPORT_SYMBOL(do_try_module_get);
    +
    #else /* !CONFIG_MODULE_UNLOAD */
    static inline void print_unload_info(struct seq_file *m, struct module *mod)
    {




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