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

[Luis Chamberlain]

On Thu, Nov 24, 2022 at 10:36:23AM +0800, Leizhen (ThunderTown) wrote:
> 
> 
> On 2022/11/23 21:28, Petr Mladek wrote:
> > 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);
> > }
> 
> Good idea. But these patches have been merged into linux-next, how about I post
> a new cleanup patch after v6.2-rc1?

You can send the cleanup now. The code doesn't change drastically, just
base it on modules-next.

  Luis