Wireshark-dev: Re: [Wireshark-dev] Enabling linux kernel jit compiler from dumpcap?

From: Martin Kaiser <lists@xxxxxxxxx>
Date: Fri, 23 Aug 2013 10:36:09 +0200
before we change it, should we remember the previous setting and restore
it when dumpcap exits?

Thus wrote Anders Broman (a.broman@xxxxxxxxxxxx):

> B�lint R�czey skrev 2013-08-22 23:02:
>> Hi,

>> I would be happier if the applications I run did not change kernel
>> configuration without my consent.
> I see your point...

>> Regarding Wireshark I would prefer suggesting "echo 1 >
>> /proc/sys/net/core/bpf_jit_enable" in the documentation
>> instead of adding code to enable JIT.
>> There may be good reasons for not enabling it by default in the Linux kernel.
> The problematic thing is that people seldom reads the documentation, the  
> setting gets reset at a reboot
> and it's easy to forget to re-enable it. The ideal thing would be if dumpcap
> - Had a preference/command line flag whether to use JIT or not.
> - If told to use it check if it was enabled or not used JIT and put it  
> back to zero if not set when starting.
> Wireshark could then default to use JIT and some warnings could be  
> displayed in the welcome screen
> and in dumpcaps help output.

> netsniff-ng activates it by default it seems.
> Regards
> Anders

>> Cheers,
>> Balint

>> 2013/8/22 Anders Broman <a.broman@xxxxxxxxxxxx>:
>>> Guy Harris skrev 2013-08-22 18:16:

>>>> On Aug 22, 2013, at 4:46 AM, Anders Broman <anders.broman@xxxxxxxxxxxx>
>>>> wrote:

>>>>> Should we add code to enable the JIT compiler from dumpcap?
>>>> Should I add code to enable the JIT compiler to libpcap while I'm at it?

>>>> Should the Linux kernel folks enable it by default?

>>>> I'm inclined to answer "yes" to all three questions.  I think the FreeBSD
>>>> JIT compiler is enabled by default.  I'm surprised that the Linux one isn't.
>>> I checked in the dumpcap code. I agree that it might be useful in libpcap
>>> too, root privileges are required to
>>> change it I think. and Yes

>>>> I'm surprised that the Linux one isn't
>>> Regards
>>> Anders

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