lkml.org 
[lkml]   [2010]   [Sep]   [9]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: perf events over (net) console?
On Thu, Sep 09, 2010 at 03:07:23PM +0200, Ingo Molnar wrote:
>
> * Peter Zijlstra <peterz@infradead.org> wrote:
>
> > On Thu, 2010-09-09 at 14:31 +0200, Harald Gustafsson wrote:
> >
> > > Sorry for being daft...
> >
> > No worries, I'm sure we all qualify at times ;-)
> >
> > > >> >
> > > >> > 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 for the pointers to more information, and yes my thoughts was
> > > more about avoiding the data copy then avoiding any processing
> > > context at all.
> >
> > Right, currently you get a single copy with mmap() + write(), once we
> > manage to fix splice() and actually provide perf-splice() you'd be
> > able to do zero-copy.
>
> I think it would also be very useful to have some sort of tooling help
> for "low overhead/impact perf recording".
>
> If there's a 'target box' and a different 'host box' (where most of
> development is done, etc.), then there might not be any NFS connection
> set up to make zero-copy file transfer easy. Doing it over ssh would add
> overhead.
>
> One possible workflow would be to run this on the target/remote box:
>
> perf remote
>
> And as long as that command is running there, it could be used from the
> development box (over a trusted local network), using something like:
>
> perf --remote <hostname> record sleep 60
> perf --remote <hostname> stat -a sleep 1
>
> these would all do the measurements on the remote box, and the resulting
> perf.data would be created on the desktop box. Communication would be
> done via some well-known port.
>
> etc.
>
> An alternative implementation would be to drive this on the assumption
> that an ssh connection can be established with the target box - but
> followup high-volume data transfer would be done over an ordinary TCP
> connection.
>
> I.e. the workflow would be even simpler, something like:
>
> perf --remote user@hostname record sleep 60
> perf --remote user@hostname stat -a sleep 1
>
> Internally it would work by executing those commands on the remote box
> via ssh, and redirecting the output via a TCP connection. (some other
> details might be needed as well for splice to be usable in such a setup)
>
> Would anyone be interested in having (and implementing ;-) this?
>
> Ingo



In the beginning this could wrap into perf record - | perf pipe | netcat
and so, until we get the splice support.


\
 
 \ /
  Last update: 2010-09-09 15:23    [from the cache]
©2003-2011 Jasper Spaans