Adding a new VFS Lttng module for performance testing

[deanraccoon]

Hi, Ralph,
    I have updated the patcheset on the latest master. And also added
a new man page for the lttng module,
Can you have a look at it ?

Ralph Böhme <slow at samba.org> 于2018年12月18日周二 上午12:50写道：
>
> Hi,
>
> sorry, looks like we dropped the ball on this one.
>
> On Wed, Oct 24, 2018 at 12:04:03PM +0800, deanraccoon wrote:
> >I think syscalls only works for local file system. When I was tuning the samba
> >ceph/glusterfs module. Neither systemtap nor bpf could help me.
>
> ah, I see. Well, you can trace arbitray functions with Systemtap, but after some
> more research I see another argument for having the ltt-ng VFS module. With
> Systemtap every enabled tracepoint that is excersized triggers a context switch
> as all metrics are gathered in the kernel by Systemtap. As a result for large
> number of enabled trace points (think: all syscalls) the performance impact on
> the process becomes significant.
>
> With ltt-ng by contrast the metrics are collected in userspace so the costly
> context switch is avoided.
>
> Can you send us an updated patchset on top of current master? We'll also need a
> manpage. I'll happily review and will help getting this integrated.
>
> -slow
>
> --
> Ralph Boehme, Samba Team                https://samba.org/
> Samba Developer, SerNet GmbH   https://sernet.de/en/samba/
> GPG-Fingerprint   FAE2C6088A24252051C559E4AA1E9B7126399E46



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