Re: [PATCH] perf_events: improve x86 event scheduling (v5)

[Frederic Weisbecker <fweisbec@gmail.com>]

On Mon, Jan 18, 2010 at 03:56:41PM +0100, Peter Zijlstra wrote:
> On Mon, 2010-01-18 at 15:45 +0100, Frederic Weisbecker wrote:
> > 
> > > > That requires to know in advance if we have hardware pmu
> > > > in the list though (can be a flag in the group).
> > > 
> > > Good point, but your proposed hw_check_constraint() call needs to know
> > > the exact same.
> > 
> > 
> > True. Whatever model we use anyway, both implement the same idea.
> 
> Hmm, we seem to already have that problem (which would indicate another
> bug in the hw-breakpoint stuff), how do you deal with
> hw_perf_{enable,disable}() for the breakpoints?


We don't have ordering constraints for breakpoints, only constraints
on the number of available registers.

So we check the constraints when a breakpoint registers. The
enable/disable then (is supposed to) always succeed on breakpoint
pmu, except for flexible breakpoints that can make it or not,
but no need to overwrite group scheduling for that.