linux-kernel - Re: [PATCH] reduce the time of finding symbols for module

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Date:   Tue, 28 Mar 2017 11:00:49 +0200 (CEST)
From:   Miroslav Benes <mbenes@...e.cz>
To:     Zhou Chengming <zhouchengming1@...wei.com>
cc:     live-patching@...r.kernel.org, linux-kernel@...r.kernel.org,
        jpoimboe@...hat.com, jeyu@...hat.com, jikos@...nel.org,
        pmladek@...e.com, huawei.libin@...wei.com
Subject: Re: [PATCH] reduce the time of finding symbols for module

Hi,

On Tue, 28 Mar 2017, Zhou Chengming wrote:

> It's reported that the time of insmoding a klp.ko for one of our
> out-tree modules is too long.
> 
> ~ time sudo insmod klp.ko
> real	0m23.799s
> user	0m0.036s
> sys	0m21.256s

Is this stable through several (>=10) runs? 23 seconds are really 
suspicious. Yes, there is a linear search through all the kallsyms in 
kallsyms_on_each_symbol(), but there are something like 70k symbols on my 
machine (that is, way less than 1M). 23 seconds are somewhat unexpected.

If it is a problem, can we fix kallsyms_on_each_symbol() and replace the 
linear search with something better? All users would benefit...

Thanks,
Miroslav