[lttng-dev] Sub-buffer multiplicity on multi-core systems

[Mathieu Desnoyers]

----- Original Message -----
> From: "Daniel Thibault" <Daniel.Thibault at drdc-rddc.gc.ca>
> To: "Mathieu Desnoyers" <mathieu.desnoyers at efficios.com>
> Cc: lttng-dev at lists.lttng.org
> Sent: Thursday, October 10, 2013 10:41:18 AM
> Subject: RE: [lttng-dev] Sub-buffer multiplicity on multi-core systems
> 
> > >    Thanks for confirming the 1:1 correspondence between channels and
> > >    files.
> > >    I wanted to make sure I understood the ins and outs properly.
> >
> > Not quite,
> >
> > It's a 1:1 correspondence between ring buffer and file.
> > 1:N correspondence between channel and ring buffers. (typically, N being
> > the number of cpus) (therefore 1:N correspondence between channel and
> > files)
> > 1:M correspondence between ring buffer and sub-buffers. (M being the number
> > of subbuffers per buffers, configurable on a per-channel basis)
> > 1:1 correspondence between sub-buffer and CTF trace packet.
> >
> > Mathieu
> 
>    I meant 1:1 correspondence between channel+cpu and file, as you said (I
>    should have stayed in bed this morning :-) ).
> 
>    In a situation where all user-space events are being traced per UID,
>    aren't the ring buffers further duplicated if there are both 32- and
>    64-bit events?  It would seem so since you will get both a
>    session/ust/uid/1000/64-bit/channel0_0 file and a
>    session/ust/uid/1000/32-bit/channel0_0 file.

Yes, this is indeed per "bitness" too.

Thanks,

Mathieu

> 
> Daniel U. Thibault
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-- 
Mathieu Desnoyers
EfficiOS Inc.
http://www.efficios.com