Re: perf events over (net) console?

From: Ingo Molnar
Date: Thu Sep 09 2010 - 07:41:07 EST



* Frederic Weisbecker <fweisbec@xxxxxxxxx> wrote:

> On Thu, Sep 09, 2010 at 01:19:01PM +0200, Peter Zijlstra wrote:
> > On Thu, 2010-09-09 at 13:06 +0200, Harald Gustafsson wrote:
> > > Hi,
> > >
> > > We would like to monitor the perf events continuously on a remote
> > > machine. Does it exist a solution (in the kernel) to direct the
> > > output to a console or maybe even a netconsole? We would like to
> > > avoid a user space application to transfer it, due to that the
> > > machine will be running a test which will heavily load it and we
> > > want to avoid as many unrelated user space tasks as possible. If
> > > not mainlined does anyone have a patch for this?
> >
> > No, and its a daft requirement.
> >
> > You need a process context anyway to read the data and send it to
> > whatever place you want it.
> >
> > Putting that in-kernel serves no purpose what so ever.
>
> But if we bring the splice support, that can be done with minimal
> userspace noise. Plus that would work with the usual sockets but not
> limited to that.

Yes. If we can transform the data over the network without it touching
disk, then that would be a sufficiently 'does not disturb other tasks'
measurement method.

Thanks,

Ingo
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