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    SubjectRe: [RFC][PATCH 7/7] perf: Optimize sw events
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    On Fri, 2010-10-15 at 11:16 +0200, Peter Zijlstra wrote:
    > On Thu, 2010-10-14 at 22:34 +0200, Peter Zijlstra wrote:
    >
    > > Index: linux-2.6/include/linux/perf_event.h
    > > ===================================================================
    > > --- linux-2.6.orig/include/linux/perf_event.h
    > > +++ linux-2.6/include/linux/perf_event.h
    > > @@ -1013,15 +1013,17 @@ static inline void perf_fetch_caller_reg
    > > static inline void
    > > perf_sw_event(u32 event_id, u64 nr, int nmi, struct pt_regs *regs, u64 addr)
    > > {
    > > - if (atomic_read(&perf_swevent_enabled[event_id])) {
    > > - struct pt_regs hot_regs;
    > > + struct pt_regs hot_regs;
    > >
    > > - if (!regs) {
    > > - perf_fetch_caller_regs(&hot_regs);
    > > - regs = &hot_regs;
    > > - }
    > > - __perf_sw_event(event_id, nr, nmi, regs, addr);
    > > + JUMP_LABEL(&perf_swevent_enabled[event_id], have_event);
    > > + return;
    > > +
    > > +have_event:
    > > + if (!regs) {
    > > + perf_fetch_caller_regs(&hot_regs);
    > > + regs = &hot_regs;
    > > }
    > > + __perf_sw_event(event_id, nr, nmi, regs, addr);
    > > }
    > >
    >
    > OK, so it appears I only compile tested this bit without jump_label
    > support, with that bit added back this horribly fails to compile like:
    >
    > In file included from /usr/src/linux-2.6/arch/x86/mm/fault.c:13:
    > /usr/src/linux-2.6/include/linux/perf_event.h: In function ‘perf_sw_event.clone.0’:
    > /usr/src/linux-2.6/include/linux/perf_event.h:1018: warning: asm operand 0 probably doesn’t match constraints
    > /usr/src/linux-2.6/include/linux/perf_event.h:1018: error: impossible constraint in ‘asm’
    >

    Ah, figured it out, it needs __attribute__((always_inline)), otherwise
    we end up with multiple keys for one label, which will clealy not work.

    I thought we had a __force_inline macro but I can't seem to find that.


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