Re: [PATCH v8 6/9] livepatch: Use kallsyms_on_each_match_symbol() to improve performance

Petr Mladek
2022-11-23T13:41:06Z

Hi,

I am sorry for the late review. I have been snowed under another
tasks.

On Wed 2022-11-02 16:49:18, Zhen Lei wrote:
> Based on the test results of kallsyms_on_each_match_symbol() and
> kallsyms_on_each_symbol(), the average performance can be improved by
> more than 1500 times.

Sounds great.

> --- a/kernel/livepatch/core.c
> +++ b/kernel/livepatch/core.c
> @@ -153,6 +153,24 @@ static int klp_find_callback(void *data, const char *name,
> return 0;
> }
>
> +static int klp_match_callback(void *data, unsigned long addr)
> +{
> + struct klp_find_arg *args = data;
> +
> + args->addr = addr;
> + args->count++;
> +
> + /*
> + * Finish the search when the symbol is found for the desired position
> + * or the position is not defined for a non-unique symbol.
> + */
> + if ((args->pos && (args->count == args->pos)) ||
> + (!args->pos && (args->count > 1)))
> + return 1;
> +
> + return 0;

This duplicates most of the klp_find_callback(). Please, call this
new function in klp_find_callback() instead of the duplicated code.
I mean to do:

static int klp_find_callback(void *data, const char *name, unsigned long addr)
{
struct klp_find_arg *args = data;

if (strcmp(args->name, name))
return 0;

return klp_match_callback(data, addr);
}

Otherwise, it looks good.

Best Regards,
Petr