On 2023/6/16 0:58, Song Liu wrote:
> On Tue, Jun 13, 2023 at 8:16 AM Petr Mladek <pmladek@xxxxxxxx> wrote:
>>
>
> [...]
>
>>
>> I agree that it is a slow path.
>>
>> Well, Zhen put a lot of effort into the optimization. I am not sure
>> what was the primary motivation. But it would be harsh to remove it
>> without asking.
>>
>> Zhen, what was the motivation for the speedup of kallsyms, please?
>>
If a large number of functions are modified, livepatch may fail. In some
actual scenarios(business), the patch needs to be activated within a limited time.
>
> I took a closer look at the code. kallsyms_on_each_match_symbol()
> is only used by livepatch. So indeed it doesn't make sense to drop
> all the optimizations by Zhen.
Yes, if CLANG has special requirements, it can be specially addressed.
I was thinking about CLANG, and I'll take a closer look at the current problem.
>
> I got another solution for this. Will send it shortly.
>
> Thanks,
> Song
>
>>
>>> OTOH, this version is simpler and should work just as
>>> well.
>>
>> Sure. But we should double check Zhen's motivation.
>>
>> Anyway, iterating over all symbols costs a lot. See also
>> the commit f5bdb34bf0c9314548f2d ("livepatch: Avoid CPU hogging
>> with cond_resched").
> .
>
--
Regards,
Zhen Lei
