Luke Browning wrote:
[email protected] wrote on 08/12/2006 01:04:30 PM:
> Arnd Bergmann wrote:
>
> >On Wednesday 06 December 2006 23:04, Maynard Johnson wrote:
> >
> >No code should ever need to look at other SPUs when performing an
> >operation on a given SPU, so we don't need to hold a global lock
> >during normal operation.
> >
> >We have two cases that need to be handled:
> >
> >- on each context unload and load (both for a full switch operation),
> > call to the profiling code with a pointer to the current context
> > and spu (context is NULL when unloading).
> >
> > If the new context is not know yet, scan its overlay table (expensive)
> > and store information about it in an oprofile private object.
Otherwise
> > just point to the currently active object, this should be really
cheap.
> >
> >- When enabling oprofile initially, scan all contexts that are currently
> > running on one of the SPUs. This is also expensive, but should happen
> > before the measurement starts so it does not impact the resulting
data.
> >
Agreed.
<snip>
> >>I'm not exactly sure what you're saying here. Are you suggesting
that a
> >>user may only be interested in acitve SPU notification and, therefore,
> >>shouldn't have to be depenent on the "standard" notification
> >>registration succeeding? There may be a case for adding a new
> >>registration function, I suppose; although, I'm not aware of any other
> >>users of the SPUFS notification mechanism besides OProfile and PDT,
and
> >>we need notification of both active and future SPU tasks. But I would
> >>not object to a new function.
> >>
> >>
> >>
> >I think what Luke was trying to get to is that notify_spus_active()
should
> >not call blocking_notifier_call_chain(), since it will notify other
users
> >as well as the newly registered one. Instead, it can simply call the
> >notifier function directly.
> >
> >
> Ah, yes. Thanks to both of you for pointing that out. I'll fix that
> and re-post.
>
> -Maynard
>
I actually was hoping to take this one step further. If the interface to
the context switch handler is something like:
switch_handler(int spu_id, from_ctx, to_ctx)
The function prototype for the switch handler is set in concrete by the
notification framework. The parameters are: struct notifier_block *,
unsigned long, void *.
The kernel extension can maintain an internal spu table of its own where it
marks the named spuid as active or not. You don't need to have a bunch of
individual calls. Internally, you can keep track of it yourself.
I think this would be nice to have, and I will look into it as I have
time. However, for the existing usage of the SPU switch notification, I
don't think it's too critical, since most users are not going to be
trying to do profiling or debugging with multiple SPU apps running
simultaneously.
Luke
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