From: "Leizhen (ThunderTown)" <thunder.leizhen@huawei.com>
To: Song Liu <song@kernel.org>, Petr Mladek <pmladek@suse.com>
Cc: Song Liu <songliubraving@meta.com>,
"live-patching@vger.kernel.org" <live-patching@vger.kernel.org>,
Josh Poimboeuf <jpoimboe@kernel.org>,
Jiri Kosina <jikos@kernel.org>, Miroslav Benes <mbenes@suse.cz>,
Joe Lawrence <joe.lawrence@redhat.com>,
Kernel Team <kernel-team@meta.com>
Subject: Re: [PATCH] livepatch: match symbols exactly in klp_find_object_symbol()
Date: Fri, 16 Jun 2023 09:23:59 +0800 [thread overview]
Message-ID: <3307943c-c842-ea52-d7b8-2f704139e645@huawei.com> (raw)
In-Reply-To: <CAPhsuW5TZPzzFefZ=d1OjVY7yBqge0XBnS9UE2xCWnoLmwj_Og@mail.gmail.com>
On 2023/6/16 0:58, Song Liu wrote:
> On Tue, Jun 13, 2023 at 8:16 AM Petr Mladek <pmladek@suse.com> 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
prev parent reply other threads:[~2023-06-16 1:24 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-06-02 23:24 [PATCH] livepatch: match symbols exactly in klp_find_object_symbol() Song Liu
2023-06-05 16:39 ` Josh Poimboeuf
2023-06-09 7:09 ` Petr Mladek
2023-06-09 16:35 ` Song Liu
2023-06-13 15:16 ` Petr Mladek
2023-06-15 16:58 ` Song Liu
2023-06-16 1:23 ` Leizhen (ThunderTown) [this message]
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