Re: Enabling linux kernel jit compiler from dumpcap?

[Martin Kaiser <lists () kaiser cx>]

before we change it, should we remember the previous setting and restore
it when dumpcap exits?

Thus wrote Anders Broman (a.broman () bredband net):

> Bálint Réczey 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 () bredband net>:
> > > Guy Harris skrev 2013-08-22 18:16:

> > > > On Aug 22, 2013, at 4:46 AM, Anders Broman <anders.broman () ericsson com>
> > > > 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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