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    SubjectRe: [PATCH] perf_events: improve x86 event scheduling (v5)
    On Mon, Jan 18, 2010 at 05:26:13PM +0100, Peter Zijlstra wrote:
    > 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.


    Right hw_perf_enable/disable have no action on breakpoint events.
    These were somehow considered as software events until now.

    That raises the question: why perf_disable() only takes care
    of hardware events? Very few software events can trigger
    between perf_disable() and perf_enable() sections though.

    May be I should handle breakpoints there.



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