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

[Peter Zijlstra]

On Mon, 2010-01-18 at 17:18 +0100, Frederic Weisbecker wrote:
> 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.

hw_perf_{enable,disable} are unrelated to groups.

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